常用类及源码分析

集合类 原理分析
Collection  
List  
Vector

扩充容量的方法 ensureCapacityHelper
很多方法都加入了synchronized同步语句,来保证线程安全
Vector中也允许元素为null
Vector现在已经基本不再使用

ArrayList

ArrayList是基于数组实现 
不是线程安全的,只能用在单线程环境下
可以通过下标索引直接查找到指定位置的元素,因此查找效率高,但每次插入或删除元素,就要大量地移动元素,插入删除元素的效率低
允许元素为null

LinkedList

LinkedList是基于双向循环链表实现的,除了可以当做链表来操作外,它还可以当做栈、队列和双端队列来使用
非线程安全的,只在单线程下适合使用
LinkedList中允许元素为null
插入删除效率高,查找效率低

Set  同Collection
HashSet  通过Map中的HashMap实现
TreeSet  通过Map中的TreeMap实现
Map  
Hashtable

Hashtable同样是基于哈希表实现的,同样每个元素是一个key-value对,其内部也是通过单链表解决冲突问题,容量不足(超过了阀值)时,同样会自动增长。
HashTable在不指定容量的情况下的默认容量为11,而HashMap为16,Hashtable不要求底层数组的容量一定要为2的整数次幂,而HashMap则要求一定为2的整数次幂。
Hashtable扩容时,将容量变为原来的2倍加1,而HashMap扩容时,将容量变为原来的2倍。
Hashtable也是JDK1.0引入的类,是线程安全的,能用于多线程环境中
Hashtable中key和value都不允许为null,而HashMap中key和value都允许为null(key只能有一个为null,而value则可以有多个为null)。

Properties  
HashMap

HashMap是基于哈希表实现的,每一个元素是一个key-value对,其内部通过单链表解决冲突问题,容量不足(超过了阀值)时,同样会自动增长
HashMap是非线程安全的,只是用于单线程环境下,多线程环境下可以采用concurrent并发包下的ConcurrentHashMap。
HashMap中key和value都允许为null。

TreeMap

TreeMap是基于红黑树实现 红黑树是一种特殊的二叉排序树
TreeMap是根据key进行排序的,它的排序和定位需要依赖比较器或覆写Comparable接口,也因此不需要key覆写hashCode方法和equals方法
就可以排除掉重复的key,而HashMap的key则需要通过覆写hashCode方法和equals方法来确保没有重复的key。
TreeMap的查询、插入、删除效率均没有HashMap高,一般只有要对key排序时才使用TreeMap。
TreeMap的key不能为null,而HashMap的key可以为null

public interface Collection <E> extends Iterable<E> {
//1添加
boolean add(E e);
boolean addAll(Collection<? extends E> c);
//2删除
boolean remove(Object o);
boolean removeAll(Collection<?> c);
void clear();
//3判断
boolean contains(Object o);
boolean containsAll(Collection<?> c);
boolean isEmpty(); //集合是否为空
//4获取
int size();
Iterator<E> iterator(); //迭代器 取出元素方式
//5其它
boolean retainAll(Collection<?> c); //取交集
Object[] toArray(); //转数组
<T> T[] toArray(T[] a); boolean equals(Object o);
int hashCode();
}
public interface Iterable<T> {
Iterator<T> iterator(); //具体集合类返回一个迭代器
} public interface Iterator<E> {
boolean hasNext(); //是否还有下个元素
E next(); //下一个元素
void remove();
}
public interface List<E> extends Collection<E> {
//其它方法与Collection中相同
//1添加
void add(int index, E element);
boolean addAll(int index, Collection<? extends E> c);
//2删除
E remove(int index);
//3修改
E set(int index, E element);
//4获取
E get(int index);
int indexOf(Object o);
int lastIndexOf(Object o);
List<E> subList(int fromIndex, int toIndex); ListIterator<E> listIterator();
ListIterator<E> listIterator(int index);
}
public class Vector <E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable{
protected Object[] elementData; //数据数组
protected int elementCount; //实际数据的数量
protected int capacityIncrement; //容量增长系数
private static final long serialVersionUID = -2767605614048989439L; //序列版本号 //四个不同的构造方法
// Vector构造函数。默认容量是10。
public Vector() {
this(10);
} //指定Vector容量大小的构造函数
public Vector(int initialCapacity) {
this(initialCapacity, 0);
} //指定Vector"容量大小"和"增长系数"的构造函数
public Vector(int initialCapacity, int capacityIncrement) {
super();
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: "+initialCapacity);
this.elementData = new Object[initialCapacity];
this.capacityIncrement = capacityIncrement;
} // 指定集合的Vector构造函数
public Vector(Collection<? extends E> c) {
elementData = c.toArray();
elementCount = elementData.length;
if (elementData.getClass() != Object[].class)
elementData = Arrays.copyOf(elementData, elementCount, Object[].class);
} //1增
// 在index位置处插入元素(obj)
public synchronized void insertElementAt(E obj, int index) {
modCount++;
if (index > elementCount) {
throw new ArrayIndexOutOfBoundsException(index
+ " > " + elementCount);
}
ensureCapacityHelper(elementCount + 1);
System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);
elementData[index] = obj;
elementCount++;
} // 将“元素obj”添加到Vector末尾
public synchronized void addElement(E obj) {
modCount++;
ensureCapacityHelper(elementCount + 1);
elementData[elementCount++] = obj;
} // 将“元素e”添加到Vector最后。
public synchronized boolean add(E e) {
modCount++;
ensureCapacityHelper(elementCount + 1);
elementData[elementCount++] = e;
return true;
} // 在index位置添加元素element
public void add(int index, E element) {
insertElementAt(element, index);
} // 将集合c添加到Vector中
public synchronized boolean addAll(Collection<? extends E> c) {
modCount++;
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityHelper(elementCount + numNew);
System.arraycopy(a, 0, elementData, elementCount, numNew);
elementCount += numNew;
return numNew != 0;
} // 从index位置开始,将集合c添加到Vector中
public synchronized boolean addAll(int index, Collection<? extends E> c) {
modCount++;
if (index < 0 || index > elementCount)
throw new ArrayIndexOutOfBoundsException(index); Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityHelper(elementCount + numNew); int numMoved = elementCount - index;
if (numMoved > 0)
System.arraycopy(elementData, index, elementData, index + numNew,
numMoved); System.arraycopy(a, 0, elementData, index, numNew);
elementCount += numNew;
return numNew != 0;
} //2删
// 删除index位置的元素
public synchronized void removeElementAt(int index) {
modCount++;
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " +
elementCount);
}
else if (index < 0) {
throw new ArrayIndexOutOfBoundsException(index);
}
int j = elementCount - index - 1;
if (j > 0) {
System.arraycopy(elementData, index + 1, elementData, index, j);
}
elementCount--;
elementData[elementCount] = null;
} // 在Vector中查找并删除元素obj 成功的话,返回true;否则,返回false。
public synchronized boolean removeElement(Object obj) {
modCount++;
int i = indexOf(obj);
if (i >= 0) {
removeElementAt(i);
return true;
}
return false;
} // 删除Vector中的全部元素
public synchronized void removeAllElements() {
modCount++;
for (int i = 0; i < elementCount; i++)
elementData[i] = null; elementCount = 0;
} // 删除Vector中的元素o
public boolean remove(Object o) {
return removeElement(o);
} // 删除index位置的元素,并返回index位置的原始值
public synchronized E remove(int index) {
modCount++;
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
E oldValue = elementData(index); int numMoved = elementCount - index - 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[--elementCount] = null; return oldValue;
} // 清空Vector
public void clear() {
removeAllElements();
} // 删除集合c的全部元素
public synchronized boolean removeAll(Collection<?> c) {
return super.removeAll(c);
} // 删除“非集合c中的元素”
public synchronized boolean retainAll(Collection<?> c) {
return super.retainAll(c);
} // 删除Vector中fromIndex到toIndex的元素
protected synchronized void removeRange(int fromIndex, int toIndex) {
modCount++;
int numMoved = elementCount - toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved); int newElementCount = elementCount - (toIndex-fromIndex);
while (elementCount != newElementCount)
elementData[--elementCount] = null;
} //3改
// 设置index位置的元素值为obj
public synchronized void setElementAt(E obj, int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " +
elementCount);
}
elementData[index] = obj;
} // 设置index位置的值为element。并返回index位置的原始值
public synchronized E set(int index, E element) {
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index); E oldValue = elementData(index);
elementData[index] = element;
return oldValue;
} //4查
// 返回“Vector的实际大小”,即Vector中元素个数
public synchronized int size() {
return elementCount;
} // 判断Vector是否为空
public synchronized boolean isEmpty() {
return elementCount == 0;
} // 返回“Vector中全部元素对应的Enumeration”
public Enumeration<E> elements() {
return new Enumeration<E>() {
int count = 0; public boolean hasMoreElements() {
return count < elementCount;
} public E nextElement() {
synchronized (Vector.this) {
if (count < elementCount) {
return elementData(count++);
}
}
throw new NoSuchElementException("Vector Enumeration");
}
};
} // 返回Vector中是否包含对象(o)
public boolean contains(Object o) {
return indexOf(o, 0) >= 0;
} // 查找并返回元素(o)在Vector中的索引值
public int indexOf(Object o) {
return indexOf(o, 0);
} // 从index位置开始向后查找元素(o) 若找到,则返回元素的索引值;否则,返回-1
public synchronized int indexOf(Object o, int index) {
if (o == null) {
for (int i = index ; i < elementCount ; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = index ; i < elementCount ; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
} // 从后向前查找元素(o)。并返回元素的索引
public synchronized int lastIndexOf(Object o) {
return lastIndexOf(o, elementCount-1);
} // 从后向前查找元素(o)。开始位置是从前向后的第index个数 若找到,则返回元素的“索引值”;否则,返回-1。
public synchronized int lastIndexOf(Object o, int index) {
if (index >= elementCount)
throw new IndexOutOfBoundsException(index + " >= "+ elementCount); if (o == null) {
for (int i = index; i >= 0; i--)
if (elementData[i]==null)
return i;
} else {
for (int i = index; i >= 0; i--)
if (o.equals(elementData[i]))
return i;
}
return -1;
} // 返回Vector中index位置的元素 若index越界,则抛出异常
public synchronized E elementAt(int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
}
return elementData(index);
} // 获取Vector中的第一个元素 若失败,则抛出异常!
public synchronized E firstElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData(0);
} // 获取Vector中的最后一个元素 若失败,则抛出异常!
public synchronized E lastElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData(elementCount - 1);
} @SuppressWarnings("unchecked")
E elementData(int index) {
return (E) elementData[index];
} // 获取index位置的元素
public synchronized E get(int index) {
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index); return elementData(index);
} // 返回Vector是否包含集合c
public synchronized boolean containsAll(Collection<?> c) {
return super.containsAll(c);
} // 获取Vector中fromIndex(包括)到toIndex(不包括)的子集
public synchronized List<E> subList(int fromIndex, int toIndex) {
return Collections.synchronizedList(super.subList(fromIndex, toIndex),
this);
} //5其它
// 返回Object数组
public synchronized Object[] toArray() {
return Arrays.copyOf(elementData, elementCount);
} // 返回Vector的模板数组。所谓模板数组,即可以将T设为任意的数据类型
@SuppressWarnings("unchecked")
public synchronized <T> T[] toArray(T[] a) {
if (a.length < elementCount)
return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass()); System.arraycopy(elementData, 0, a, 0, elementCount); if (a.length > elementCount)
a[elementCount] = null; return a;
} // 将数组Vector的全部元素都拷贝到数组anArray中
public synchronized void copyInto(Object[] anArray) {
System.arraycopy(elementData, 0, anArray, 0, elementCount);
} // 将当前容量值设为实际元素个数
public synchronized void trimToSize() {
modCount++;
int oldCapacity = elementData.length;
if (elementCount < oldCapacity) {
elementData = Arrays.copyOf(elementData, elementCount);
}
} // 确定Vector的容量
public synchronized void ensureCapacity(int minCapacity) {
if (minCapacity > 0) {
modCount++;
ensureCapacityHelper(minCapacity);
}
} // 确认“Vector容量”的帮助函数
private void ensureCapacityHelper(int minCapacity) {
if (minCapacity - elementData.length > 0)
grow(minCapacity);
} private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; // 当Vector的容量不足以容纳当前的全部元素,增加容量大小。
// 若 容量增量系数>0(即capacityIncrement>0),则将容量增大当capacityIncrement
// 否则,将容量增大一倍。
private void grow(int minCapacity) {
int oldCapacity = elementData.length;
int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
capacityIncrement : oldCapacity);
if (newCapacity - minCapacity < 0)
newCapacity = minCapacity;
if (newCapacity - MAX_ARRAY_SIZE > 0)
newCapacity = hugeCapacity(minCapacity);
elementData = Arrays.copyOf(elementData, newCapacity);
} private static int hugeCapacity(int minCapacity) {
if (minCapacity < 0) // overflow
throw new OutOfMemoryError();
return (minCapacity > MAX_ARRAY_SIZE) ?
Integer.MAX_VALUE :
MAX_ARRAY_SIZE;
} // 设置容量值为 newSize
public synchronized void setSize(int newSize) {
modCount++;
if (newSize > elementCount) {
ensureCapacityHelper(newSize);
} else {
for (int i = newSize ; i < elementCount ; i++) {
elementData[i] = null;
}
}
elementCount = newSize;
} // 返回“Vector的总的容量”
public synchronized int capacity() {
return elementData.length;
} public synchronized Object clone() {
try {
@SuppressWarnings("unchecked")
Vector<E> v = (Vector<E>) super.clone();
v.elementData = Arrays.copyOf(elementData, elementCount);
v.modCount = 0;
return v;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
} public synchronized boolean equals(Object o) {
return super.equals(o);
} public synchronized int hashCode() {
return super.hashCode();
} public synchronized String toString() {
return super.toString();
} //写入函数
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
final java.io.ObjectOutputStream.PutField fields = s.putFields();
final Object[] data;
synchronized (this) {
fields.put("capacityIncrement", capacityIncrement);
fields.put("elementCount", elementCount);
data = elementData.clone();
}
fields.put("elementData", data);
s.writeFields();
} public synchronized ListIterator<E> listIterator(int index) {
if (index < 0 || index > elementCount)
throw new IndexOutOfBoundsException("Index: "+index);
return new ListItr(index);
} public synchronized ListIterator<E> listIterator() {
return new ListItr(0);
} public synchronized Iterator<E> iterator() {
return new Itr();
} private class Itr implements Iterator<E> {
int cursor; // index of next element to return
int lastRet = -1; // index of last element returned; -1 if no such
int expectedModCount = modCount; public boolean hasNext() {
return cursor != elementCount;
} public E next() {
synchronized (Vector.this) {
checkForComodification();
int i = cursor;
if (i >= elementCount)
throw new NoSuchElementException();
cursor = i + 1;
return elementData(lastRet = i);
}
} public void remove() {
if (lastRet == -1)
throw new IllegalStateException();
synchronized (Vector.this) {
checkForComodification();
Vector.this.remove(lastRet);
expectedModCount = modCount;
}
cursor = lastRet;
lastRet = -1;
} final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
} final class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
super();
cursor = index;
} public boolean hasPrevious() {
return cursor != 0;
} public int nextIndex() {
return cursor;
} public int previousIndex() {
return cursor - 1;
} public E previous() {
synchronized (Vector.this) {
checkForComodification();
int i = cursor - 1;
if (i < 0)
throw new NoSuchElementException();
cursor = i;
return elementData(lastRet = i);
}
} public void set(E e) {
if (lastRet == -1)
throw new IllegalStateException();
synchronized (Vector.this) {
checkForComodification();
Vector.this.set(lastRet, e);
}
} public void add(E e) {
int i = cursor;
synchronized (Vector.this) {
checkForComodification();
Vector.this.add(i, e);
expectedModCount = modCount;
}
cursor = i + 1;
lastRet = -1;
}
}
}
public class LinkedList<E> extends AbstractSequentialList<E> implements List<E>, Deque<E>, Cloneable, java.io.Serializable{
transient int size = 0; //LinkedList中元素个数
transient Node<E> first; //链表的表头
transient Node<E> last; ////链表的末尾 // 默认构造函数:创建一个空的链表
public LinkedList() {
} //创建一个包含“集合”的LinkedList
public LinkedList(Collection<? extends E> c) {
this();
addAll(c);
} //1增
// 将元素添加到LinkedList的起始位置
private void linkFirst(E e) {
final Node<E> f = first;
final Node<E> newNode = new Node<>(null, e, f);
first = newNode;
if (f == null)
last = newNode;
else
f.prev = newNode;
size++;
modCount++;
} // 将元素添加到LinkedList的结束位置
void linkLast(E e) {
final Node<E> l = last;
final Node<E> newNode = new Node<>(l, e, null);
last = newNode;
if (l == null)
first = newNode;
else
l.next = newNode;
size++;
modCount++;
} void linkBefore(E e, Node<E> succ) {
final Node<E> pred = succ.prev;
final Node<E> newNode = new Node<>(pred, e, succ);
succ.prev = newNode;
if (pred == null)
first = newNode;
else
pred.next = newNode;
size++;
modCount++;
} // 将元素添加到LinkedList的起始位置
public void addFirst(E e) {
linkFirst(e);
} // 将元素添加到LinkedList的结束位置
public void addLast(E e) {
linkLast(e);
} // 将元素(E)添加到LinkedList结束位置
public boolean add(E e) {
linkLast(e);
return true;
} //从双向链表的末尾开始,将“集合(c)”添加到双向链表中
public boolean addAll(Collection<? extends E> c) {
return addAll(size, c);
} //从双向链表的index开始,将“集合(c)”添加到双向链表中
public boolean addAll(int index, Collection<? extends E> c) {
checkPositionIndex(index); Object[] a = c.toArray();
int numNew = a.length;
if (numNew == 0)
return false; Node<E> pred, succ;
if (index == size) {
succ = null;
pred = last;
} else {
succ = node(index);
pred = succ.prev;
} for (Object o : a) {
@SuppressWarnings("unchecked") E e = (E) o;
Node<E> newNode = new Node<>(pred, e, null);
if (pred == null)
first = newNode;
else
pred.next = newNode;
pred = newNode;
} if (succ == null) {
last = pred;
} else {
pred.next = succ;
succ.prev = pred;
} size += numNew;
modCount++;
return true;
} // 在index前添加节点,且节点的值为element
public void add(int index, E element) {
checkPositionIndex(index); if (index == size)
linkLast(element);
else
linkBefore(element, node(index));
} // 将e添加双向链表末尾
public boolean offer(E e) {
return add(e);
} // 将e添加双向链表开头
public boolean offerFirst(E e) {
addFirst(e);
return true;
} // 将e添加双向链表末尾
public boolean offerLast(E e) {
addLast(e);
return true;
} // 将e插入到双向链表开头
public void push(E e) {
addFirst(e);
} //2删 private E unlinkFirst(Node<E> f) {
final E element = f.item;
final Node<E> next = f.next;
f.item = null;
f.next = null;
first = next;
if (next == null)
last = null;
else
next.prev = null;
size--;
modCount++;
return element;
} private E unlinkLast(Node<E> l) {
final E element = l.item;
final Node<E> prev = l.prev;
l.item = null;
l.prev = null;
last = prev;
if (prev == null)
first = null;
else
prev.next = null;
size--;
modCount++;
return element;
} E unlink(Node<E> x) {
final E element = x.item;
final Node<E> next = x.next;
final Node<E> prev = x.prev; if (prev == null) {
first = next;
} else {
prev.next = next;
x.prev = null;
} if (next == null) {
last = prev;
} else {
next.prev = prev;
x.next = null;
} x.item = null;
size--;
modCount++;
return element;
} // 删除LinkedList的第一个元素
public E removeFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return unlinkFirst(f);
} // 删除LinkedList的最后一个元素
public E removeLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return unlinkLast(l);
} // 从LinkedList中删除元素(o) 从链表开始查找,如存在元素(o)则删除该元素并返回true 否则,返回false。
public boolean remove(Object o) {
if (o == null) {
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item)) {
unlink(x);
return true;
}
}
}
return false;
} // 清空双向链表
public void clear() {
for (Node<E> x = first; x != null; ) {
// 从表头开始,逐个向后遍历;对遍历到的节点执行一下操作:
// 设置前一个节点为null
// 设置当前节点的内容为null
// 设置后一个节点为“新的当前节点”
Node<E> next = x.next;
x.item = null;
x.next = null;
x.prev = null;
x = next;
}
first = last = null;
size = 0;
modCount++;
} // 删除index位置的节点
public E remove(int index) {
checkElementIndex(index);
return unlink(node(index));
} // 删除并返回第一个节点 若LinkedList的大小为0,则返回null
public E poll() {
final Node<E> f = first;
return (f == null) ? null : unlinkFirst(f);
} // 删除并返回第一个节点 若LinkedList的大小为0,则返回null
public E pollFirst() {
final Node<E> f = first;
return (f == null) ? null : unlinkFirst(f);
} // 删除并返回最后一个节点 若LinkedList的大小为0,则返回null
public E pollLast() {
final Node<E> l = last;
return (l == null) ? null : unlinkLast(l);
} // 删除并返回第一个节点
public E pop() {
return removeFirst();
} // 从LinkedList开始向后查找,删除第一个值为元素(o)的节点
public boolean removeFirstOccurrence(Object o) {
return remove(o);
} // 从LinkedList末尾向前查找,删除第一个值为元素(o)的节点
public boolean removeLastOccurrence(Object o) {
if (o == null) {
for (Node<E> x = last; x != null; x = x.prev) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
for (Node<E> x = last; x != null; x = x.prev) {
if (o.equals(x.item)) {
unlink(x);
return true;
}
}
}
return false;
} public E remove() {
return removeFirst();
} //3改
// 设置index位置对应的节点的值为element
public E set(int index, E element) {
checkElementIndex(index);
Node<E> x = node(index);
E oldVal = x.item;
x.item = element;
return oldVal;
} //4查
// 获取LinkedList的第一个元素
public E getFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return f.item;
} // 获取LinkedList的最后一个元素
public E getLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return l.item;
} // 判断LinkedList是否包含元素(o)
public boolean contains(Object o) {
return indexOf(o) != -1;
} // 返回LinkedList的大小
public int size() {
return size;
} // 返回LinkedList指定位置的元素
public E get(int index) {
checkElementIndex(index);
return node(index).item;
} // 获取双向链表中指定位置的节点
Node<E> node(int index) {
// 获取index处的节点。
// 若index < 双向链表长度的1/2,则从前先后查找;
// 否则,从后向前查找。
if (index < (size >> 1)) {
Node<E> x = first;
for (int i = 0; i < index; i++)
x = x.next;
return x;
} else {
Node<E> x = last;
for (int i = size - 1; i > index; i--)
x = x.prev;
return x;
}
} // 从前向后查找,返回“值为对象(o)的节点对应的索引” 不存在就返回-1
public int indexOf(Object o) {
int index = 0;
if (o == null) {
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null)
return index;
index++;
}
} else {
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item))
return index;
index++;
}
}
return -1;
} // 从后向前查找,返回“值为对象(o)的节点对应的索引” 不存在就返回-1
public int lastIndexOf(Object o) {
int index = size;
if (o == null) {
for (Node<E> x = last; x != null; x = x.prev) {
index--;
if (x.item == null)
return index;
}
} else {
for (Node<E> x = last; x != null; x = x.prev) {
index--;
if (o.equals(x.item))
return index;
}
}
return -1;
} // 返回第一个节点 若LinkedList的大小为0,则返回null
public E peek() {
final Node<E> f = first;
return (f == null) ? null : f.item;
} // 返回第一个节点 若LinkedList的大小为0,则抛出异常
public E element() {
return getFirst();
} // 返回第一个节点 若LinkedList的大小为0,则返回null
public E peekFirst() {
final Node<E> f = first;
return (f == null) ? null : f.item;
} // 返回最后一个节点 若LinkedList的大小为0,则返回null
public E peekLast() {
final Node<E> l = last;
return (l == null) ? null : l.item;
} //5其它
private boolean isElementIndex(int index) {
return index >= 0 && index < size;
} private boolean isPositionIndex(int index) {
return index >= 0 && index <= size;
} private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+size;
} private void checkElementIndex(int index) {
if (!isElementIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
} private void checkPositionIndex(int index) {
if (!isPositionIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
} public ListIterator<E> listIterator(int index) {
checkPositionIndex(index);
return new ListItr(index);
} // List迭代器
private class ListItr implements ListIterator<E> {
private Node<E> lastReturned = null;
private Node<E> next;
private int nextIndex;
private int expectedModCount = modCount; ListItr(int index) {
next = (index == size) ? null : node(index);
nextIndex = index;
} public boolean hasNext() {
return nextIndex < size;
} public E next() {
checkForComodification();
if (!hasNext())
throw new NoSuchElementException(); lastReturned = next;
next = next.next;
nextIndex++;
return lastReturned.item;
} public boolean hasPrevious() {
return nextIndex > 0;
} public E previous() {
checkForComodification();
if (!hasPrevious())
throw new NoSuchElementException(); lastReturned = next = (next == null) ? last : next.prev;
nextIndex--;
return lastReturned.item;
} public int nextIndex() {
return nextIndex;
} public int previousIndex() {
return nextIndex - 1;
} public void remove() {
checkForComodification();
if (lastReturned == null)
throw new IllegalStateException(); Node<E> lastNext = lastReturned.next;
unlink(lastReturned);
if (next == lastReturned)
next = lastNext;
else
nextIndex--;
lastReturned = null;
expectedModCount++;
} public void set(E e) {
if (lastReturned == null)
throw new IllegalStateException();
checkForComodification();
lastReturned.item = e;
} public void add(E e) {
checkForComodification();
lastReturned = null;
if (next == null)
linkLast(e);
else
linkBefore(e, next);
nextIndex++;
expectedModCount++;
} final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
} // 双向链表的节点所对应的数据结构 包含3部分:上一节点,下一节点,当前节点值
private static class Node<E> {
E item; //当前节点所包含的值
Node<E> next; // 下一个节点
Node<E> prev; //上一个节点 Node(Node<E> prev, E element, Node<E> next) {
this.item = element;
this.next = next;
this.prev = prev;
}
} // 反向迭代器
public Iterator<E> descendingIterator() {
return new DescendingIterator();
} private class DescendingIterator implements Iterator<E> {
private final ListItr itr = new ListItr(size());
public boolean hasNext() {
return itr.hasPrevious();
}
public E next() {
return itr.previous();
}
public void remove() {
itr.remove();
}
} @SuppressWarnings("unchecked")
private LinkedList<E> superClone() {
try {
return (LinkedList<E>) super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
} public Object clone() {
LinkedList<E> clone = superClone(); clone.first = clone.last = null;
clone.size = 0;
clone.modCount = 0; for (Node<E> x = first; x != null; x = x.next)
clone.add(x.item); return clone;
} public Object[] toArray() {
Object[] result = new Object[size];
int i = 0;
for (Node<E> x = first; x != null; x = x.next)
result[i++] = x.item;
return result;
} @SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
if (a.length < size)
a = (T[])java.lang.reflect.Array.newInstance(
a.getClass().getComponentType(), size);
int i = 0;
Object[] result = a;
for (Node<E> x = first; x != null; x = x.next)
result[i++] = x.item; if (a.length > size)
a[size] = null; return a;
} private static final long serialVersionUID = 876323262645176354L; private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// Write out any hidden serialization magic
s.defaultWriteObject(); // Write out size
s.writeInt(size); // Write out all elements in the proper order.
for (Node<E> x = first; x != null; x = x.next)
s.writeObject(x.item);
} @SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in any hidden serialization magic
s.defaultReadObject(); // Read in size
int size = s.readInt(); // Read in all elements in the proper order.
for (int i = 0; i < size; i++)
linkLast((E)s.readObject());
}
}
public class ArrayList<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable{
private static final long serialVersionUID = 8683452581122892189L; // 序列版本号
private static final int DEFAULT_CAPACITY = 10;
private static final Object[] EMPTY_ELEMENTDATA = {};
private transient Object[] elementData; //保存数据数组
private int size; // ArrayList中实际数据的数量 // ArrayList无参构造函数。默认容量是10。
public ArrayList() {
super();
this.elementData = EMPTY_ELEMENTDATA;
} // ArrayList带容量大小的构造函数。
public ArrayList(int initialCapacity) {
super();
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
this.elementData = new Object[initialCapacity];
} // 创建一个包含collection的ArrayList
public ArrayList(Collection<? extends E> c) {
elementData = c.toArray();
size = elementData.length;
if (elementData.getClass() != Object[].class)
elementData = Arrays.copyOf(elementData, size, Object[].class);
} //1增
// 将e添加到ArrayList中
public boolean add(E e) {
ensureCapacityInternal(size + 1);
elementData[size++] = e;
return true;
} // 将e添加到ArrayList的指定位置
public void add(int index, E element) {
rangeCheckForAdd(index); ensureCapacityInternal(size + 1);
System.arraycopy(elementData, index, elementData, index + 1,
size - index);
elementData[index] = element;
size++;
} // 将集合c追加到ArrayList中
public boolean addAll(Collection<? extends E> c) {
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityInternal(size + numNew);
System.arraycopy(a, 0, elementData, size, numNew);
size += numNew;
return numNew != 0;
} // 从index位置开始,将集合c添加到ArrayList
public boolean addAll(int index, Collection<? extends E> c) {
rangeCheckForAdd(index); Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityInternal(size + numNew); int numMoved = size - index;
if (numMoved > 0)
System.arraycopy(elementData, index, elementData, index + numNew,
numMoved); System.arraycopy(a, 0, elementData, index, numNew);
size += numNew;
return numNew != 0;
} //2删
// 删除ArrayList指定位置的元素
public E remove(int index) {
rangeCheck(index); modCount++;
E oldValue = elementData(index); int numMoved = size - index - 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[--size] = null;
return oldValue;
} // 删除ArrayList的指定元素
public boolean remove(Object o) {
if (o == null) {
for (int index = 0; index < size; index++)
if (elementData[index] == null) {
fastRemove(index);
return true;
}
} else {
for (int index = 0; index < size; index++)
if (o.equals(elementData[index])) {
fastRemove(index);
return true;
}
}
return false;
} // 快速删除第index个元素
private void fastRemove(int index) {
modCount++;
int numMoved = size - index - 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[--size] = null;
} // 清空ArrayList,将全部的元素设为null
public void clear() {
modCount++; for (int i = 0; i < size; i++)
elementData[i] = null; size = 0;
} // 删除fromIndex到toIndex之间的全部元素
protected void removeRange(int fromIndex, int toIndex) {
modCount++;
int numMoved = size - toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved); int newSize = size - (toIndex-fromIndex);
for (int i = newSize; i < size; i++) {
elementData[i] = null;
}
size = newSize;
} //3改
// 设置index位置的值为element
public E set(int index, E element) {
rangeCheck(index); E oldValue = elementData(index);
elementData[index] = element;
return oldValue;
} //4查
// 返回ArrayList的实际大小
public int size() {
return size;
} //返回ArrayList是否为空
public boolean isEmpty() {
return size == 0;
} // ArrayList是否包含Object(o)
public boolean contains(Object o) {
return indexOf(o) >= 0;
} // 正向查找,返回元素的索引值
public int indexOf(Object o) {
if (o == null) {
for (int i = 0; i < size; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = 0; i < size; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
} // 反向查找,返回元素的索引值
public int lastIndexOf(Object o) {
if (o == null) {
for (int i = size-1; i >= 0; i--)
if (elementData[i]==null)
return i;
} else {
for (int i = size-1; i >= 0; i--)
if (o.equals(elementData[i]))
return i;
}
return -1;
} // 获取index位置的元素值
@SuppressWarnings("unchecked")
E elementData(int index) {
return (E) elementData[index];
} public E get(int index) {
rangeCheck(index);
return elementData(index);
} //5其它
public Object[] toArray() {
return Arrays.copyOf(elementData, size);
} @SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
if (a.length < size)
return (T[]) Arrays.copyOf(elementData, size, a.getClass());
System.arraycopy(elementData, 0, a, 0, size);
if (a.length > size)
a[size] = null;
return a;
} // 将当前容量值设为实际元素个数
public void trimToSize() {
modCount++;
if (size < elementData.length) {
elementData = Arrays.copyOf(elementData, size);
}
} public void ensureCapacity(int minCapacity) {
int minExpand = (elementData != EMPTY_ELEMENTDATA)
? 0
: DEFAULT_CAPACITY; if (minCapacity > minExpand) {
ensureExplicitCapacity(minCapacity);
}
} private void ensureCapacityInternal(int minCapacity) {
if (elementData == EMPTY_ELEMENTDATA) {
minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity);
} ensureExplicitCapacity(minCapacity);
} // 确定ArrarList的容量
private void ensureExplicitCapacity(int minCapacity) {
modCount++;
if (minCapacity - elementData.length > 0)
grow(minCapacity);
} private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; private void grow(int minCapacity) {
int oldCapacity = elementData.length;
int newCapacity = oldCapacity + (oldCapacity >> 1);
if (newCapacity - minCapacity < 0)
newCapacity = minCapacity;
if (newCapacity - MAX_ARRAY_SIZE > 0)
newCapacity = hugeCapacity(minCapacity);
elementData = Arrays.copyOf(elementData, newCapacity);
} private static int hugeCapacity(int minCapacity) {
if (minCapacity < 0)
throw new OutOfMemoryError();
return (minCapacity > MAX_ARRAY_SIZE) ?
Integer.MAX_VALUE :
MAX_ARRAY_SIZE;
} public Object clone() {
try {
@SuppressWarnings("unchecked")
ArrayList<E> v = (ArrayList<E>) super.clone();
v.elementData = Arrays.copyOf(elementData, size);
v.modCount = 0;
return v;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
} private void rangeCheck(int index) {
if (index >= size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
} private void rangeCheckForAdd(int index) {
if (index > size || index < 0)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
} private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+size;
} public boolean removeAll(Collection<?> c) {
return batchRemove(c, false);
} public boolean retainAll(Collection<?> c) {
return batchRemove(c, true);
} private boolean batchRemove(Collection<?> c, boolean complement) {
final Object[] elementData = this.elementData;
int r = 0, w = 0;
boolean modified = false;
try {
for (; r < size; r++)
if (c.contains(elementData[r]) == complement)
elementData[w++] = elementData[r];
} finally {
if (r != size) {
System.arraycopy(elementData, r,
elementData, w,
size - r);
w += size - r;
}
if (w != size) {
for (int i = w; i < size; i++)
elementData[i] = null;
modCount += size - w;
size = w;
modified = true;
}
}
return modified;
} private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException{
int expectedModCount = modCount;
s.defaultWriteObject(); s.writeInt(size); for (int i=0; i<size; i++) {
s.writeObject(elementData[i]);
} if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
} private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
elementData = EMPTY_ELEMENTDATA; s.defaultReadObject();
s.readInt(); if (size > 0) {
ensureCapacityInternal(size); Object[] a = elementData;
for (int i=0; i<size; i++) {
a[i] = s.readObject();
}
}
} public ListIterator<E> listIterator(int index) {
if (index < 0 || index > size)
throw new IndexOutOfBoundsException("Index: "+index);
return new ListItr(index);
} public ListIterator<E> listIterator() {
return new ListItr(0);
} public Iterator<E> iterator() {
return new Itr();
} private class Itr implements Iterator<E> {
int cursor;
int lastRet = -1;
int expectedModCount = modCount; public boolean hasNext() {
return cursor != size;
} @SuppressWarnings("unchecked")
public E next() {
checkForComodification();
int i = cursor;
if (i >= size)
throw new NoSuchElementException();
Object[] elementData = ArrayList.this.elementData;
if (i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i + 1;
return (E) elementData[lastRet = i];
} public void remove() {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification(); try {
ArrayList.this.remove(lastRet);
cursor = lastRet;
lastRet = -1;
expectedModCount = modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
} final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
} private class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
super();
cursor = index;
} public boolean hasPrevious() {
return cursor != 0;
} public int nextIndex() {
return cursor;
} public int previousIndex() {
return cursor - 1;
} @SuppressWarnings("unchecked")
public E previous() {
checkForComodification();
int i = cursor - 1;
if (i < 0)
throw new NoSuchElementException();
Object[] elementData = ArrayList.this.elementData;
if (i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i;
return (E) elementData[lastRet = i];
} public void set(E e) {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification(); try {
ArrayList.this.set(lastRet, e);
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
} public void add(E e) {
checkForComodification(); try {
int i = cursor;
ArrayList.this.add(i, e);
cursor = i + 1;
lastRet = -1;
expectedModCount = modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
} public List<E> subList(int fromIndex, int toIndex) {
subListRangeCheck(fromIndex, toIndex, size);
return new SubList(this, 0, fromIndex, toIndex);
} static void subListRangeCheck(int fromIndex, int toIndex, int size) {
if (fromIndex < 0)
throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
if (toIndex > size)
throw new IndexOutOfBoundsException("toIndex = " + toIndex);
if (fromIndex > toIndex)
throw new IllegalArgumentException("fromIndex(" + fromIndex +
") > toIndex(" + toIndex + ")");
} private class SubList extends AbstractList<E> implements RandomAccess {
private final AbstractList<E> parent;
private final int parentOffset;
private final int offset;
int size; SubList(AbstractList<E> parent,
int offset, int fromIndex, int toIndex) {
this.parent = parent;
this.parentOffset = fromIndex;
this.offset = offset + fromIndex;
this.size = toIndex - fromIndex;
this.modCount = ArrayList.this.modCount;
} public E set(int index, E e) {
rangeCheck(index);
checkForComodification();
E oldValue = ArrayList.this.elementData(offset + index);
ArrayList.this.elementData[offset + index] = e;
return oldValue;
} public E get(int index) {
rangeCheck(index);
checkForComodification();
return ArrayList.this.elementData(offset + index);
} public int size() {
checkForComodification();
return this.size;
} public void add(int index, E e) {
rangeCheckForAdd(index);
checkForComodification();
parent.add(parentOffset + index, e);
this.modCount = parent.modCount;
this.size++;
} public E remove(int index) {
rangeCheck(index);
checkForComodification();
E result = parent.remove(parentOffset + index);
this.modCount = parent.modCount;
this.size--;
return result;
} protected void removeRange(int fromIndex, int toIndex) {
checkForComodification();
parent.removeRange(parentOffset + fromIndex,
parentOffset + toIndex);
this.modCount = parent.modCount;
this.size -= toIndex - fromIndex;
} public boolean addAll(Collection<? extends E> c) {
return addAll(this.size, c);
} public boolean addAll(int index, Collection<? extends E> c) {
rangeCheckForAdd(index);
int cSize = c.size();
if (cSize==0)
return false; checkForComodification();
parent.addAll(parentOffset + index, c);
this.modCount = parent.modCount;
this.size += cSize;
return true;
} public Iterator<E> iterator() {
return listIterator();
} public ListIterator<E> listIterator(final int index) {
checkForComodification();
rangeCheckForAdd(index);
final int offset = this.offset; return new ListIterator<E>() {
int cursor = index;
int lastRet = -1;
int expectedModCount = ArrayList.this.modCount; public boolean hasNext() {
return cursor != SubList.this.size;
} @SuppressWarnings("unchecked")
public E next() {
checkForComodification();
int i = cursor;
if (i >= SubList.this.size)
throw new NoSuchElementException();
Object[] elementData = ArrayList.this.elementData;
if (offset + i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i + 1;
return (E) elementData[offset + (lastRet = i)];
} public boolean hasPrevious() {
return cursor != 0;
} @SuppressWarnings("unchecked")
public E previous() {
checkForComodification();
int i = cursor - 1;
if (i < 0)
throw new NoSuchElementException();
Object[] elementData = ArrayList.this.elementData;
if (offset + i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i;
return (E) elementData[offset + (lastRet = i)];
} public int nextIndex() {
return cursor;
} public int previousIndex() {
return cursor - 1;
} public void remove() {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification(); try {
SubList.this.remove(lastRet);
cursor = lastRet;
lastRet = -1;
expectedModCount = ArrayList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
} public void set(E e) {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification(); try {
ArrayList.this.set(offset + lastRet, e);
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
} public void add(E e) {
checkForComodification(); try {
int i = cursor;
SubList.this.add(i, e);
cursor = i + 1;
lastRet = -1;
expectedModCount = ArrayList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
} final void checkForComodification() {
if (expectedModCount != ArrayList.this.modCount)
throw new ConcurrentModificationException();
}
};
} public List<E> subList(int fromIndex, int toIndex) {
subListRangeCheck(fromIndex, toIndex, size);
return new SubList(this, offset, fromIndex, toIndex);
} private void rangeCheck(int index) {
if (index < 0 || index >= this.size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
} private void rangeCheckForAdd(int index) {
if (index < 0 || index > this.size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
} private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+this.size;
} private void checkForComodification() {
if (ArrayList.this.modCount != this.modCount)
throw new ConcurrentModificationException();
}
}
}
public class HashSet<E> extends AbstractSet<E> implements Set<E>, Cloneable, java.io.Serializable{
static final long serialVersionUID = -5024744406713321676L;
private transient HashMap<E,Object> map;
private static final Object PRESENT = new Object(); public HashSet() {
map = new HashMap<>();
} public HashSet(Collection<? extends E> c) {
map = new HashMap<>(Math.max((int) (c.size()/.75f) + 1, 16));
addAll(c);
} public HashSet(int initialCapacity, float loadFactor) {
map = new HashMap<>(initialCapacity, loadFactor);
} public HashSet(int initialCapacity) {
map = new HashMap<>(initialCapacity);
} HashSet(int initialCapacity, float loadFactor, boolean dummy) {
map = new LinkedHashMap<>(initialCapacity, loadFactor);
} //1增
public boolean add(E e) {
return map.put(e, PRESENT)==null;
} //2删
public boolean remove(Object o) {
return map.remove(o)==PRESENT;
} public void clear() {
map.clear();
} //3改 //4查
public int size() {
return map.size();
} public boolean isEmpty() {
return map.isEmpty();
} public boolean contains(Object o) {
return map.containsKey(o);
} public Iterator<E> iterator() {
return map.keySet().iterator();
} public Object clone() {
try {
HashSet<E> newSet = (HashSet<E>) super.clone();
newSet.map = (HashMap<E, Object>) map.clone();
return newSet;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
} private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
s.defaultWriteObject(); s.writeInt(map.capacity());
s.writeFloat(map.loadFactor()); s.writeInt(map.size()); for (E e : map.keySet())
s.writeObject(e);
} private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject(); int capacity = s.readInt();
float loadFactor = s.readFloat();
map = (((HashSet)this) instanceof LinkedHashSet ?
new LinkedHashMap<E,Object>(capacity, loadFactor) :
new HashMap<E,Object>(capacity, loadFactor)); int size = s.readInt(); for (int i=0; i<size; i++) {
E e = (E) s.readObject();
map.put(e, PRESENT);
}
}
}
public class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>, Cloneable, java.io.Serializable{
private transient NavigableMap<E,Object> m;
private static final Object PRESENT = new Object(); TreeSet(NavigableMap<E,Object> m) {
this.m = m;
} public TreeSet() {
this(new TreeMap<E,Object>());
} public TreeSet(Comparator<? super E> comparator) {
this(new TreeMap<>(comparator));
} public TreeSet(Collection<? extends E> c) {
this();
addAll(c);
} public TreeSet(SortedSet<E> s) {
this(s.comparator());
addAll(s);
} public Iterator<E> iterator() {
return m.navigableKeySet().iterator();
} public Iterator<E> descendingIterator() {
return m.descendingKeySet().iterator();
} public NavigableSet<E> descendingSet() {
return new TreeSet<>(m.descendingMap());
} public int size() {
return m.size();
} public boolean isEmpty() {
return m.isEmpty();
} public boolean contains(Object o) {
return m.containsKey(o);
} public boolean add(E e) {
return m.put(e, PRESENT)==null;
} public boolean remove(Object o) {
return m.remove(o)==PRESENT;
} public void clear() {
m.clear();
} public boolean addAll(Collection<? extends E> c) {
if (m.size()==0 && c.size() > 0 &&
c instanceof SortedSet &&
m instanceof TreeMap) {
SortedSet<? extends E> set = (SortedSet<? extends E>) c;
TreeMap<E,Object> map = (TreeMap<E, Object>) m;
Comparator<? super E> cc = (Comparator<? super E>) set.comparator();
Comparator<? super E> mc = map.comparator();
if (cc==mc || (cc != null && cc.equals(mc))) {
map.addAllForTreeSet(set, PRESENT);
return true;
}
}
return super.addAll(c);
} public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
E toElement, boolean toInclusive) {
return new TreeSet<>(m.subMap(fromElement, fromInclusive,
toElement, toInclusive));
} public NavigableSet<E> headSet(E toElement, boolean inclusive) {
return new TreeSet<>(m.headMap(toElement, inclusive));
} public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
return new TreeSet<>(m.tailMap(fromElement, inclusive));
} public SortedSet<E> subSet(E fromElement, E toElement) {
return subSet(fromElement, true, toElement, false);
} public SortedSet<E> headSet(E toElement) {
return headSet(toElement, false);
} public SortedSet<E> tailSet(E fromElement) {
return tailSet(fromElement, true);
} public Comparator<? super E> comparator() {
return m.comparator();
} public E first() {
return m.firstKey();
} public E last() {
return m.lastKey();
} public E lower(E e) {
return m.lowerKey(e);
} public E floor(E e) {
return m.floorKey(e);
} public E ceiling(E e) {
return m.ceilingKey(e);
} public E higher(E e) {
return m.higherKey(e);
} public E pollFirst() {
Map.Entry<E,?> e = m.pollFirstEntry();
return (e == null) ? null : e.getKey();
} public E pollLast() {
Map.Entry<E,?> e = m.pollLastEntry();
return (e == null) ? null : e.getKey();
} public Object clone() {
TreeSet<E> clone = null;
try {
clone = (TreeSet<E>) super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError();
} clone.m = new TreeMap<>(m);
return clone;
} private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
s.defaultWriteObject();
s.writeObject(m.comparator());
s.writeInt(m.size());
for (E e : m.keySet())
s.writeObject(e);
} private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject(); Comparator<? super E> c = (Comparator<? super E>) s.readObject(); TreeMap<E,Object> tm;
if (c==null)
tm = new TreeMap<>();
else
tm = new TreeMap<>(c);
m = tm; int size = s.readInt(); tm.readTreeSet(size, s, PRESENT);
} private static final long serialVersionUID = -2479143000061671589L;
}
public interface Map<K,V> {
//1增
V put(K key, V value);//返回前一个和key关联的值,如果没有返回null. //2删
void clear(); //清空map集合
V remove(Object key); //根据指定的key删除这个键值对 //3改 //4查
boolean isEmpty();
boolean containsKey(Object key);
boolean containsValue(Object value);
int size();
V get(Object key); void putAll(Map<? extends K, ? extends V> m);
Set<K> keySet();
Collection<V> values();
Set<Map.Entry<K, V>> entrySet();
interface Entry<K,V> {
K getKey();
V getValue();
V setValue(V value);
boolean equals(Object o);
int hashCode();
} boolean equals(Object o);
int hashCode(); }
public class HashMap<K,V> extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable {
static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // 默认的初始容量(容量为HashMap中槽的数目)是16,且实际容量必须是2的整数次幂。
static final int MAXIMUM_CAPACITY = 1 << 30; // 最大容量(必须是2的幂且小于2的30次方,传入容量过大将被这个值替换)
static final float DEFAULT_LOAD_FACTOR = 0.75f; // 默认加载因子为0.75
static final Entry<?,?>[] EMPTY_TABLE = {};
transient Entry<K,V>[] table = (Entry<K,V>[]) EMPTY_TABLE; // 存储数据的Entry数组 每一个Entry本质上是一个单向链表
transient int size; // HashMap的底层数组中已用槽的数量
int threshold; // HashMap的阈值,用于判断是否需要调整HashMap的容量(threshold = 容量*加载因子)
final float loadFactor; // 加载因子实际大小
transient int modCount; // HashMap被改变的次数
static final int ALTERNATIVE_HASHING_THRESHOLD_DEFAULT = Integer.MAX_VALUE; private static class Holder { static final int ALTERNATIVE_HASHING_THRESHOLD; static {
String altThreshold = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction(
"jdk.map.althashing.threshold")); int threshold;
try {
threshold = (null != altThreshold)
? Integer.parseInt(altThreshold)
: ALTERNATIVE_HASHING_THRESHOLD_DEFAULT; if (threshold == -1) {
threshold = Integer.MAX_VALUE;
} if (threshold < 0) {
throw new IllegalArgumentException("value must be positive integer.");
}
} catch(IllegalArgumentException failed) {
throw new Error("Illegal value for 'jdk.map.althashing.threshold'", failed);
} ALTERNATIVE_HASHING_THRESHOLD = threshold;
}
} transient int hashSeed = 0; // 指定“容量大小”和“加载因子”的构造函数
public HashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal initial capacity: " +
initialCapacity);
if (initialCapacity > MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException("Illegal load factor: " +
loadFactor); this.loadFactor = loadFactor;
threshold = initialCapacity;
init();
} // 指定“容量大小”的构造函数
public HashMap(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
} // 默认构造函数
public HashMap() {
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
} // 包含“子Map”的构造函数
public HashMap(Map<? extends K, ? extends V> m) {
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
inflateTable(threshold);
putAllForCreate(m);
} private static int roundUpToPowerOf2(int number) {
return number >= MAXIMUM_CAPACITY
? MAXIMUM_CAPACITY
: (number > 1) ? Integer.highestOneBit((number - 1) << 1) : 1;
} private void inflateTable(int toSize) {
int capacity = roundUpToPowerOf2(toSize); threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
table = new Entry[capacity];
initHashSeedAsNeeded(capacity);
} void init() {
} final boolean initHashSeedAsNeeded(int capacity) {
boolean currentAltHashing = hashSeed != 0;
boolean useAltHashing = sun.misc.VM.isBooted() &&
(capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
boolean switching = currentAltHashing ^ useAltHashing;
if (switching) {
hashSeed = useAltHashing
? sun.misc.Hashing.randomHashSeed(this)
: 0;
}
return switching;
} //求hash值的方法,重新计算hash值
final int hash(Object k) {
int h = hashSeed;
if (0 != h && k instanceof String) {
return sun.misc.Hashing.stringHash32((String) k);
} h ^= k.hashCode();
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
} // 返回h在数组中的索引值,这里用&代替取模,旨在提升效率
// h & (length-1)保证返回值的小于length
static int indexFor(int h, int length) {
return h & (length-1);
} public int size() {
return size;
} public boolean isEmpty() {
return size == 0;
} // 获取key对应的value
public V get(Object key) {
if (key == null)
return getForNullKey();
Entry<K,V> entry = getEntry(key); return null == entry ? null : entry.getValue();
} // 获取“key为null”的元素的值
// HashMap将“key为null”的元素存储在table[0]位置,但不一定是该链表的第一个位置!
private V getForNullKey() {
if (size == 0) {
return null;
}
for (Entry<K,V> e = table[0]; e != null; e = e.next) {
if (e.key == null)
return e.value;
}
return null;
} // HashMap是否包含key
public boolean containsKey(Object key) {
return getEntry(key) != null;
} // 返回“键为key”的键值对
final Entry<K,V> getEntry(Object key) {
if (size == 0) {
return null;
}
// 获取key的hash值
int hash = (key == null) ? 0 : hash(key);
// 在“该hash值对应的链表”上查找“键值等于key”的元素
for (Entry<K,V> e = table[indexFor(hash, table.length)];
e != null;
e = e.next) {
Object k;
//判断key是否相同
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
return e;
}
return null;
} // 将“key-value”添加到HashMap中
public V put(K key, V value) {
if (table == EMPTY_TABLE) {
inflateTable(threshold);
}
// 若“key为null”,则将该键值对添加到table[0]中。
if (key == null)
return putForNullKey(value);
// 若“key不为null”,则计算该key的哈希值,然后将其添加到该哈希值对应的链表中。
int hash = hash(key);
int i = indexFor(hash, table.length);
for (Entry<K,V> e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
V oldValue = e.value;
e.value = value;
e.recordAccess(this);
return oldValue;
}
} modCount++;
//将key-value添加到table[i]处
addEntry(hash, key, value, i);
return null;
} //将“key为null”键值对添加到table[0]位置
private V putForNullKey(V value) {
for (Entry<K,V> e = table[0]; e != null; e = e.next) {
if (e.key == null) {
V oldValue = e.value;
e.value = value;
e.recordAccess(this);
return oldValue;
}
}
modCount++;
addEntry(0, null, value, 0);
return null;
} // 创建HashMap对应的“添加方法”,
// 它和put()不同。putForCreate()是内部方法,它被构造函数等调用,用来创建HashMap
// 而put()是对外提供的往HashMap中添加元素的方法。
private void putForCreate(K key, V value) {
int hash = null == key ? 0 : hash(key);
int i = indexFor(hash, table.length); for (Entry<K,V> e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
e.value = value;
return;
}
} createEntry(hash, key, value, i);
} // 将“m”中的全部元素都添加到HashMap中。
// 该方法被内部的构造HashMap的方法所调用。
private void putAllForCreate(Map<? extends K, ? extends V> m) {
for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
putForCreate(e.getKey(), e.getValue());
} // 重新调整HashMap的大小,newCapacity是调整后的容量
void resize(int newCapacity) {
Entry[] oldTable = table;
int oldCapacity = oldTable.length;
//如果就容量已经达到了最大值,则不能再扩容,直接返回
if (oldCapacity == MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return;
} // 新建一个HashMap,将“旧HashMap”的全部元素添加到“新HashMap”中,
// 然后,将“新HashMap”赋值给“旧HashMap”。
Entry[] newTable = new Entry[newCapacity];
transfer(newTable, initHashSeedAsNeeded(newCapacity));
table = newTable;
threshold = (int)Math.min(newCapacity * loadFactor, MAXIMUM_CAPACITY + 1);
} // 将HashMap中的全部元素都添加到newTable中
void transfer(Entry[] newTable, boolean rehash) {
int newCapacity = newTable.length;
for (Entry<K,V> e : table) {
while(null != e) {
Entry<K,V> next = e.next;
if (rehash) {
e.hash = null == e.key ? 0 : hash(e.key);
}
int i = indexFor(e.hash, newCapacity);
e.next = newTable[i];
newTable[i] = e;
e = next;
}
}
} // 将"m"的全部元素都添加到HashMap中
public void putAll(Map<? extends K, ? extends V> m) {
int numKeysToBeAdded = m.size();
if (numKeysToBeAdded == 0)
return; if (table == EMPTY_TABLE) {
inflateTable((int) Math.max(numKeysToBeAdded * loadFactor, threshold));
} if (numKeysToBeAdded > threshold) {
int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
if (targetCapacity > MAXIMUM_CAPACITY)
targetCapacity = MAXIMUM_CAPACITY;
int newCapacity = table.length;
while (newCapacity < targetCapacity)
newCapacity <<= 1;
if (newCapacity > table.length)
resize(newCapacity);
} for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
put(e.getKey(), e.getValue());
} // 删除“键为key”元素
public V remove(Object key) {
Entry<K,V> e = removeEntryForKey(key);
return (e == null ? null : e.value);
} final Entry<K,V> removeEntryForKey(Object key) {
if (size == 0) {
return null;
}
// 获取哈希值。若key为null,则哈希值为0;否则调用hash()进行计算
int hash = (key == null) ? 0 : hash(key);
int i = indexFor(hash, table.length);
Entry<K,V> prev = table[i];
Entry<K,V> e = prev; // 删除链表中“键为key”的元素
// 本质是“删除单向链表中的节点”
while (e != null) {
Entry<K,V> next = e.next;
Object k;
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
modCount++;
size--;
if (prev == e)
table[i] = next;
else
prev.next = next;
e.recordRemoval(this);
return e;
}
prev = e;
e = next;
} return e;
} // 删除“键值对”
final Entry<K,V> removeMapping(Object o) {
if (size == 0 || !(o instanceof Map.Entry))
return null; Map.Entry<K,V> entry = (Map.Entry<K,V>) o;
Object key = entry.getKey();
int hash = (key == null) ? 0 : hash(key);
int i = indexFor(hash, table.length);
Entry<K,V> prev = table[i];
Entry<K,V> e = prev; while (e != null) {
Entry<K,V> next = e.next;
if (e.hash == hash && e.equals(entry)) {
modCount++;
size--;
if (prev == e)
table[i] = next;
else
prev.next = next;
e.recordRemoval(this);
return e;
}
prev = e;
e = next;
} return e;
} // 清空HashMap,将所有的元素设为null
public void clear() {
modCount++;
Arrays.fill(table, null);
size = 0;
} // 是否包含“值为value”的元素
public boolean containsValue(Object value) {
if (value == null)
return containsNullValue(); Entry[] tab = table;
for (int i = 0; i < tab.length ; i++)
for (Entry e = tab[i] ; e != null ; e = e.next)
if (value.equals(e.value))
return true;
return false;
} // 是否包含null值
private boolean containsNullValue() {
Entry[] tab = table;
for (int i = 0; i < tab.length ; i++)
for (Entry e = tab[i] ; e != null ; e = e.next)
if (e.value == null)
return true;
return false;
} // 克隆一个HashMap,并返回Object对象
public Object clone() {
HashMap<K,V> result = null;
try {
result = (HashMap<K,V>)super.clone();
} catch (CloneNotSupportedException e) {
}
if (result.table != EMPTY_TABLE) {
result.inflateTable(Math.min(
(int) Math.min(
size * Math.min(1 / loadFactor, 4.0f),
HashMap.MAXIMUM_CAPACITY),
table.length));
}
result.entrySet = null;
result.modCount = 0;
result.size = 0;
result.init();
result.putAllForCreate(this); return result;
} // Entry是单向链表 它是 “HashMap链式存储法”对应的链表。
static class Entry<K,V> implements Map.Entry<K,V> {
final K key;
V value;
Entry<K,V> next; // 指向下一个节点
int hash; // 构造函数 输入参数包括"哈希值(h)", "键(k)", "值(v)", "下一节点(n)"
Entry(int h, K k, V v, Entry<K,V> n) {
value = v;
next = n;
key = k;
hash = h;
} public final K getKey() {
return key;
} public final V getValue() {
return value;
} public final V setValue(V newValue) {
V oldValue = value;
value = newValue;
return oldValue;
} // 判断两个Entry是否相等
// 若两个Entry的“key”和“value”都相等,则返回true。
// 否则,返回false
public final boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
Object k1 = getKey();
Object k2 = e.getKey();
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
Object v1 = getValue();
Object v2 = e.getValue();
if (v1 == v2 || (v1 != null && v1.equals(v2)))
return true;
}
return false;
} public final int hashCode() {
return Objects.hashCode(getKey()) ^ Objects.hashCode(getValue());
} public final String toString() {
return getKey() + "=" + getValue();
} // 当向HashMap中添加元素时,绘调用recordAccess()。
void recordAccess(HashMap<K,V> m) {
} // 当从HashMap中删除元素时,绘调用recordRemoval()
void recordRemoval(HashMap<K,V> m) {
}
} // 新增Entry。将“key-value”插入指定位置,bucketIndex是位置索引
void addEntry(int hash, K key, V value, int bucketIndex) {
if ((size >= threshold) && (null != table[bucketIndex])) {
resize(2 * table.length);
hash = (null != key) ? hash(key) : 0;
bucketIndex = indexFor(hash, table.length);
} createEntry(hash, key, value, bucketIndex);
} // 创建Entry。将“key-value”插入指定位置
void createEntry(int hash, K key, V value, int bucketIndex) {
Entry<K,V> e = table[bucketIndex];
table[bucketIndex] = new Entry<>(hash, key, value, e);
size++;
} // HashIterator是HashMap迭代器的抽象出来的父类,实现了公共函数
private abstract class HashIterator<E> implements Iterator<E> {
Entry<K,V> next; // next entry to return
int expectedModCount; // For fast-fail
int index; // current slot
Entry<K,V> current; // current entry HashIterator() {
expectedModCount = modCount;
if (size > 0) { // advance to first entry
Entry[] t = table;
while (index < t.length && (next = t[index++]) == null)
;
}
} public final boolean hasNext() {
return next != null;
} final Entry<K,V> nextEntry() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Entry<K,V> e = next;
if (e == null)
throw new NoSuchElementException(); if ((next = e.next) == null) {
Entry[] t = table;
while (index < t.length && (next = t[index++]) == null)
;
}
current = e;
return e;
} public void remove() {
if (current == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Object k = current.key;
current = null;
HashMap.this.removeEntryForKey(k);
expectedModCount = modCount;
}
} private final class ValueIterator extends HashIterator<V> {
public V next() {
return nextEntry().value;
}
} private final class KeyIterator extends HashIterator<K> {
public K next() {
return nextEntry().getKey();
}
} private final class EntryIterator extends HashIterator<Map.Entry<K,V>> {
public Map.Entry<K,V> next() {
return nextEntry();
}
} Iterator<K> newKeyIterator() {
return new KeyIterator();
}
Iterator<V> newValueIterator() {
return new ValueIterator();
}
Iterator<Map.Entry<K,V>> newEntryIterator() {
return new EntryIterator();
} private transient Set<Map.Entry<K,V>> entrySet = null; public Set<K> keySet() {
Set<K> ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
} // Key对应的集合
// KeySet继承于AbstractSet,说明该集合中没有重复的Key
private final class KeySet extends AbstractSet<K> {
public Iterator<K> iterator() {
return newKeyIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return HashMap.this.removeEntryForKey(o) != null;
}
public void clear() {
HashMap.this.clear();
}
} // 返回“value集合”,实际上返回的是一个Values对象
public Collection<V> values() {
Collection<V> vs = values;
return (vs != null ? vs : (values = new Values()));
} // “value集合”
// Values继承于AbstractCollection,不同于“KeySet继承于AbstractSet”,
// Values中的元素能够重复。因为不同的key可以指向相同的value。
private final class Values extends AbstractCollection<V> {
public Iterator<V> iterator() {
return newValueIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
HashMap.this.clear();
}
} // 返回“HashMap的Entry集合”
public Set<Map.Entry<K,V>> entrySet() {
return entrySet0();
} // 返回“HashMap的Entry集合”,它实际是返回一个EntrySet对象
private Set<Map.Entry<K,V>> entrySet0() {
Set<Map.Entry<K,V>> es = entrySet;
return es != null ? es : (entrySet = new EntrySet());
} // EntrySet对应的集合
// EntrySet继承于AbstractSet,说明该集合中没有重复的EntrySet。
private final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
public Iterator<Map.Entry<K,V>> iterator() {
return newEntryIterator();
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<K,V> e = (Map.Entry<K,V>) o;
Entry<K,V> candidate = getEntry(e.getKey());
return candidate != null && candidate.equals(e);
}
public boolean remove(Object o) {
return removeMapping(o) != null;
}
public int size() {
return size;
}
public void clear() {
HashMap.this.clear();
}
} // java.io.Serializable的写入函数
// 将HashMap的“总的容量,实际容量,所有的Entry”都写入到输出流中
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
if (table==EMPTY_TABLE) {
s.writeInt(roundUpToPowerOf2(threshold));
} else {
s.writeInt(table.length);
}
s.writeInt(size);
if (size > 0) {
for(Map.Entry<K,V> e : entrySet0()) {
s.writeObject(e.getKey());
s.writeObject(e.getValue());
}
}
} private static final long serialVersionUID = 362498820763181265L; // java.io.Serializable的读取函数:根据写入方式读出
// 将HashMap的“总的容量,实际容量,所有的Entry”依次读出
private void readObject(java.io.ObjectInputStream s)
throws IOException, ClassNotFoundException {
s.defaultReadObject();
if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
throw new InvalidObjectException("Illegal load factor: " +
loadFactor);
} table = (Entry<K,V>[]) EMPTY_TABLE; s.readInt(); // ignored. int mappings = s.readInt();
if (mappings < 0)
throw new InvalidObjectException("Illegal mappings count: " +
mappings); int capacity = (int) Math.min(
mappings * Math.min(1 / loadFactor, 4.0f),
HashMap.MAXIMUM_CAPACITY); if (mappings > 0) {
inflateTable(capacity);
} else {
threshold = capacity;
} init(); for (int i = 0; i < mappings; i++) {
K key = (K) s.readObject();
V value = (V) s.readObject();
putForCreate(key, value);
}
} // 返回“HashMap总的容量”
int capacity() { return table.length; }
// 返回“HashMap的加载因子”
float loadFactor() { return loadFactor; }
}
public class Hashtable<K,V> extends Dictionary<K,V> implements Map<K,V>, Cloneable, java.io.Serializable {

    private transient Entry<?,?>[] table; //保存key-value的数组 Hashtable同样采用单链表解决冲突,每一个Entry本质上是一个单向链表
private transient int count; //键值对的数量
private int threshold; //阈值,用于判断是否需要调整Hashtable的容量(threshold = 容量*加载因子)
private float loadFactor; //加载因子
private transient int modCount = 0; //Hashtable被改变的次数,用于fail-fast机制的实现
private static final long serialVersionUID = 1421746759512286392L; //序列版本号 // 指定“容量大小”和“加载因子”的构造函数
public Hashtable(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException("Illegal Load: "+loadFactor); if (initialCapacity==0)
initialCapacity = 1;
this.loadFactor = loadFactor;
table = new Entry<?,?>[initialCapacity];
threshold = (int)Math.min(initialCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
} // 指定“容量大小”的构造函数
public Hashtable(int initialCapacity) {
this(initialCapacity, 0.75f);
} // 默认构造函数 容量大小是11;加载因子是0.75
public Hashtable() {
this(11, 0.75f);
} // 包含“子Map”的构造函数
public Hashtable(Map<? extends K, ? extends V> t) {
this(Math.max(2*t.size(), 11), 0.75f);
putAll(t);
} public synchronized int size() {
return count;
} public synchronized boolean isEmpty() {
return count == 0;
} // 返回“所有key”的枚举对象
public synchronized Enumeration<K> keys() {
return this.<K>getEnumeration(KEYS);
} // 返回“所有value”的枚举对象
public synchronized Enumeration<V> elements() {
return this.<V>getEnumeration(VALUES);
} // 判断Hashtable是否包含“值(value)”
public synchronized boolean contains(Object value) {
//注意,Hashtable中的value不能是null,若是null的话,抛出异常!
if (value == null) {
throw new NullPointerException();
} // 从后向前遍历table数组中的元素(Entry)
// 对于每个Entry(单向链表),逐个遍历,判断节点的值是否等于value
Entry<?,?> tab[] = table;
for (int i = tab.length ; i-- > 0 ;) {
for (Entry<?,?> e = tab[i] ; e != null ; e = e.next) {
if (e.value.equals(value)) {
return true;
}
}
}
return false;
} public boolean containsValue(Object value) {
return contains(value);
} //判断Hashtable是否包含key
public synchronized boolean containsKey(Object key) {
Entry<?,?> tab[] = table;
//计算hash值,直接用key的hashCode代替
int hash = key.hashCode();
// 计算在数组中的索引值
int index = (hash & 0x7FFFFFFF) % tab.length;
// 找到“key对应的Entry(链表)”,然后在链表中找出“哈希值”和“键值”与key都相等的元素
for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
return true;
}
}
return false;
} // 返回key对应的value,没有的话返回null
@SuppressWarnings("unchecked")
public synchronized V get(Object key) {
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
return (V)e.value;
}
}
return null;
} private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; //调整Hashtable的长度,将长度变成原来的2倍+1
@SuppressWarnings("unchecked")
protected void rehash() {
int oldCapacity = table.length;
Entry<?,?>[] oldMap = table; //创建新容量大小的Entry数组
int newCapacity = (oldCapacity << 1) + 1;
if (newCapacity - MAX_ARRAY_SIZE > 0) {
if (oldCapacity == MAX_ARRAY_SIZE)
// Keep running with MAX_ARRAY_SIZE buckets
return;
newCapacity = MAX_ARRAY_SIZE;
}
Entry<?,?>[] newMap = new Entry<?,?>[newCapacity]; modCount++;
threshold = (int)Math.min(newCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
table = newMap; //将“旧的Hashtable”中的元素复制到“新的Hashtable”中
for (int i = oldCapacity ; i-- > 0 ;) {
for (Entry<K,V> old = (Entry<K,V>)oldMap[i] ; old != null ; ) {
Entry<K,V> e = old;
old = old.next; int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = (Entry<K,V>)newMap[index];
newMap[index] = e;
}
}
} private void addEntry(int hash, K key, V value, int index) {
modCount++; Entry<?,?> tab[] = table;
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash(); tab = table;
hash = key.hashCode();
index = (hash & 0x7FFFFFFF) % tab.length;
} // Creates the new entry.
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>) tab[index];
tab[index] = new Entry<>(hash, key, value, e);
count++;
} // 将“key-value”添加到Hashtable中
public synchronized V put(K key, V value) {
// Hashtable中不能插入value为null的元素!!!
if (value == null) {
throw new NullPointerException();
} // 若“Hashtable中已存在键为key的键值对”,则用“新的value”替换“旧的value”
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> entry = (Entry<K,V>)tab[index];
for(; entry != null ; entry = entry.next) {
if ((entry.hash == hash) && entry.key.equals(key)) {
V old = entry.value;
entry.value = value;
return old;
}
} // 若“Hashtable中不存在键为key的键值对”,
addEntry(hash, key, value, index);
return null;
} // 删除Hashtable中键为key的元素
public synchronized V remove(Object key) {
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for(Entry<K,V> prev = null ; e != null ; prev = e, e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
V oldValue = e.value;
e.value = null;
return oldValue;
}
}
return null;
} // 将“Map(t)”的中全部元素逐一添加到Hashtable中
public synchronized void putAll(Map<? extends K, ? extends V> t) {
for (Map.Entry<? extends K, ? extends V> e : t.entrySet())
put(e.getKey(), e.getValue());
} // 清空Hashtable
// 将Hashtable的table数组的值全部设为null
public synchronized void clear() {
Entry<?,?> tab[] = table;
modCount++;
for (int index = tab.length; --index >= 0; )
tab[index] = null;
count = 0;
} // 克隆一个Hashtable,并以Object的形式返回。
public synchronized Object clone() {
try {
Hashtable<?,?> t = (Hashtable<?,?>)super.clone();
t.table = new Entry<?,?>[table.length];
for (int i = table.length ; i-- > 0 ; ) {
t.table[i] = (table[i] != null)
? (Entry<?,?>) table[i].clone() : null;
}
t.keySet = null;
t.entrySet = null;
t.values = null;
t.modCount = 0;
return t;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError(e);
}
} /**
* Returns a string representation of this <tt>Hashtable</tt> object
* in the form of a set of entries, enclosed in braces and separated
* by the ASCII characters "<tt>,&nbsp;</tt>" (comma and space). Each
* entry is rendered as the key, an equals sign <tt>=</tt>, and the
* associated element, where the <tt>toString</tt> method is used to
* convert the key and element to strings.
*
* @return a string representation of this hashtable
*/
public synchronized String toString() {
int max = size() - 1;
if (max == -1)
return "{}"; StringBuilder sb = new StringBuilder();
Iterator<Map.Entry<K,V>> it = entrySet().iterator(); sb.append('{');
for (int i = 0; ; i++) {
Map.Entry<K,V> e = it.next();
K key = e.getKey();
V value = e.getValue();
sb.append(key == this ? "(this Map)" : key.toString());
sb.append('=');
sb.append(value == this ? "(this Map)" : value.toString()); if (i == max)
return sb.append('}').toString();
sb.append(", ");
}
} // 获取Hashtable的枚举类对象
private <T> Enumeration<T> getEnumeration(int type) {
if (count == 0) {
return Collections.emptyEnumeration();
} else {
return new Enumerator<>(type, false);
}
} // 获取Hashtable的迭代器
private <T> Iterator<T> getIterator(int type) {
if (count == 0) {
return Collections.emptyIterator();
} else {
return new Enumerator<>(type, true);
}
} private transient volatile Set<K> keySet; // Hashtable的“key的集合”。它是一个Set,没有重复元素
private transient volatile Set<Map.Entry<K,V>> entrySet; // Hashtable的“key-value的集合”。它是一个Set,没有重复元素
private transient volatile Collection<V> values; // Hashtable的“key-value的集合”。它是一个Collection,可以有重复元素 // 返回一个被synchronizedSet封装后的KeySet对象
public Set<K> keySet() {
if (keySet == null)
keySet = Collections.synchronizedSet(new KeySet(), this);
return keySet;
} // Hashtable的Key的Set集合。
private class KeySet extends AbstractSet<K> {
public Iterator<K> iterator() {
return getIterator(KEYS);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return Hashtable.this.remove(o) != null;
}
public void clear() {
Hashtable.this.clear();
}
} // 返回一个被synchronizedSet封装后的EntrySet对象
public Set<Map.Entry<K,V>> entrySet() {
if (entrySet==null)
entrySet = Collections.synchronizedSet(new EntrySet(), this);
return entrySet;
} // Hashtable的Entry的Set集合。
private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
public Iterator<Map.Entry<K,V>> iterator() {
return getIterator(ENTRIES);
} public boolean add(Map.Entry<K,V> o) {
return super.add(o);
} public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
Object key = entry.getKey();
Entry<?,?>[] tab = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length; for (Entry<?,?> e = tab[index]; e != null; e = e.next)
if (e.hash==hash && e.equals(entry))
return true;
return false;
} public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
Object key = entry.getKey();
Entry<?,?>[] tab = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length; @SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for(Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
if (e.hash==hash && e.equals(entry)) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[index] = e.next; count--;
e.value = null;
return true;
}
}
return false;
} public int size() {
return count;
} public void clear() {
Hashtable.this.clear();
}
} // 返回一个被synchronizedCollection封装后的ValueCollection对象
public Collection<V> values() {
if (values==null)
values = Collections.synchronizedCollection(new ValueCollection(),
this);
return values;
} // Hashtable的value的Collection集合。
private class ValueCollection extends AbstractCollection<V> {
public Iterator<V> iterator() {
return getIterator(VALUES);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
Hashtable.this.clear();
}
} public synchronized boolean equals(Object o) {
if (o == this)
return true; if (!(o instanceof Map))
return false;
Map<?,?> t = (Map<?,?>) o;
if (t.size() != size())
return false; try {
Iterator<Map.Entry<K,V>> i = entrySet().iterator();
while (i.hasNext()) {
Map.Entry<K,V> e = i.next();
K key = e.getKey();
V value = e.getValue();
if (value == null) {
if (!(t.get(key)==null && t.containsKey(key)))
return false;
} else {
if (!value.equals(t.get(key)))
return false;
}
}
} catch (ClassCastException unused) {
return false;
} catch (NullPointerException unused) {
return false;
} return true;
} // 计算Entry的hashCode
// 若 Hashtable的实际大小为0 或者 加载因子<0,则返回0。
// 否则,返回“Hashtable中的每个Entry的key和value的异或值 的总和”。
public synchronized int hashCode() {
int h = 0;
if (count == 0 || loadFactor < 0)
return h; loadFactor = -loadFactor;
Entry<?,?>[] tab = table;
for (Entry<?,?> entry : tab) {
while (entry != null) {
h += entry.hashCode();
entry = entry.next;
}
} loadFactor = -loadFactor; return h;
} @Override
public synchronized V getOrDefault(Object key, V defaultValue) {
V result = get(key);
return (null == result) ? defaultValue : result;
} @SuppressWarnings("unchecked")
@Override
public synchronized void forEach(BiConsumer<? super K, ? super V> action) {
Objects.requireNonNull(action); // explicit check required in case
// table is empty.
final int expectedModCount = modCount; Entry<?, ?>[] tab = table;
for (Entry<?, ?> entry : tab) {
while (entry != null) {
action.accept((K)entry.key, (V)entry.value);
entry = entry.next; if (expectedModCount != modCount) {
throw new ConcurrentModificationException();
}
}
}
} @SuppressWarnings("unchecked")
@Override
public synchronized void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
Objects.requireNonNull(function); // explicit check required in case
// table is empty.
final int expectedModCount = modCount; Entry<K, V>[] tab = (Entry<K, V>[])table;
for (Entry<K, V> entry : tab) {
while (entry != null) {
entry.value = Objects.requireNonNull(
function.apply(entry.key, entry.value));
entry = entry.next; if (expectedModCount != modCount) {
throw new ConcurrentModificationException();
}
}
}
} @Override
public synchronized V putIfAbsent(K key, V value) {
Objects.requireNonNull(value); // Makes sure the key is not already in the hashtable.
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> entry = (Entry<K,V>)tab[index];
for (; entry != null; entry = entry.next) {
if ((entry.hash == hash) && entry.key.equals(key)) {
V old = entry.value;
if (old == null) {
entry.value = value;
}
return old;
}
} addEntry(hash, key, value, index);
return null;
} @Override
public synchronized boolean remove(Object key, Object value) {
Objects.requireNonNull(value); Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
if ((e.hash == hash) && e.key.equals(key) && e.value.equals(value)) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
e.value = null;
return true;
}
}
return false;
} @Override
public synchronized boolean replace(K key, V oldValue, V newValue) {
Objects.requireNonNull(oldValue);
Objects.requireNonNull(newValue);
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (; e != null; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
if (e.value.equals(oldValue)) {
e.value = newValue;
return true;
} else {
return false;
}
}
}
return false;
} @Override
public synchronized V replace(K key, V value) {
Objects.requireNonNull(value);
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (; e != null; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
V oldValue = e.value;
e.value = value;
return oldValue;
}
}
return null;
} @Override
public synchronized V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
Objects.requireNonNull(mappingFunction); Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (; e != null; e = e.next) {
if (e.hash == hash && e.key.equals(key)) {
// Hashtable not accept null value
return e.value;
}
} V newValue = mappingFunction.apply(key);
if (newValue != null) {
addEntry(hash, key, newValue, index);
} return newValue;
} @Override
public synchronized V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction); Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash && e.key.equals(key)) {
V newValue = remappingFunction.apply(key, e.value);
if (newValue == null) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
} else {
e.value = newValue;
}
return newValue;
}
}
return null;
} @Override
public synchronized V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction); Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash && Objects.equals(e.key, key)) {
V newValue = remappingFunction.apply(key, e.value);
if (newValue == null) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
} else {
e.value = newValue;
}
return newValue;
}
} V newValue = remappingFunction.apply(key, null);
if (newValue != null) {
addEntry(hash, key, newValue, index);
} return newValue;
} @Override
public synchronized V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction); Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash && e.key.equals(key)) {
V newValue = remappingFunction.apply(e.value, value);
if (newValue == null) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
} else {
e.value = newValue;
}
return newValue;
}
} if (value != null) {
addEntry(hash, key, value, index);
} return value;
} private void writeObject(java.io.ObjectOutputStream s)
throws IOException {
Entry<Object, Object> entryStack = null; synchronized (this) {
// Write out the length, threshold, loadfactor
s.defaultWriteObject(); // Write out length, count of elements
s.writeInt(table.length);
s.writeInt(count); // Stack copies of the entries in the table
for (int index = 0; index < table.length; index++) {
Entry<?,?> entry = table[index]; while (entry != null) {
entryStack =
new Entry<>(0, entry.key, entry.value, entryStack);
entry = entry.next;
}
}
} // Write out the key/value objects from the stacked entries
while (entryStack != null) {
s.writeObject(entryStack.key);
s.writeObject(entryStack.value);
entryStack = entryStack.next;
}
} private void readObject(java.io.ObjectInputStream s)
throws IOException, ClassNotFoundException {
s.defaultReadObject(); int origlength = s.readInt();
int elements = s.readInt(); int length = (int)(elements * loadFactor) + (elements / 20) + 3;
if (length > elements && (length & 1) == 0)
length--;
if (origlength > 0 && length > origlength)
length = origlength;
table = new Entry<?,?>[length];
threshold = (int)Math.min(length * loadFactor, MAX_ARRAY_SIZE + 1);
count = 0; // Read the number of elements and then all the key/value objects
for (; elements > 0; elements--) {
@SuppressWarnings("unchecked")
K key = (K)s.readObject();
@SuppressWarnings("unchecked")
V value = (V)s.readObject();
// synch could be eliminated for performance
reconstitutionPut(table, key, value);
}
} private void reconstitutionPut(Entry<?,?>[] tab, K key, V value)
throws StreamCorruptedException
{
if (value == null) {
throw new java.io.StreamCorruptedException();
}
// Makes sure the key is not already in the hashtable.
// This should not happen in deserialized version.
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
throw new java.io.StreamCorruptedException();
}
}
// Creates the new entry.
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
tab[index] = new Entry<>(hash, key, value, e);
count++;
} // Hashtable的Entry节点,它本质上是一个单向链表。
private static class Entry<K,V> implements Map.Entry<K,V> {
final int hash;
final K key;
V value;
Entry<K,V> next;// 指向的下一个Entry,即链表的下一个节点 protected Entry(int hash, K key, V value, Entry<K,V> next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
} @SuppressWarnings("unchecked")
protected Object clone() {
return new Entry<>(hash, key, value,
(next==null ? null : (Entry<K,V>) next.clone()));
} public K getKey() {
return key;
} public V getValue() {
return value;
} public V setValue(V value) {
if (value == null)
throw new NullPointerException(); V oldValue = this.value;
this.value = value;
return oldValue;
} public boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> e = (Map.Entry<?,?>)o; return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
(value==null ? e.getValue()==null : value.equals(e.getValue()));
} public int hashCode() {
return hash ^ Objects.hashCode(value);
} public String toString() {
return key.toString()+"="+value.toString();
}
} // Types of Enumerations/Iterations
private static final int KEYS = 0;
private static final int VALUES = 1;
private static final int ENTRIES = 2; // Enumerator的作用是提供了“通过elements()遍历Hashtable的接口” 和 “通过entrySet()遍历Hashtable的接口”。
private class Enumerator<T> implements Enumeration<T>, Iterator<T> {
Entry<?,?>[] table = Hashtable.this.table;
int index = table.length;
Entry<?,?> entry;
Entry<?,?> lastReturned;
int type; boolean iterator;
protected int expectedModCount = modCount;// 在将Enumerator当作迭代器使用时会用到,用来实现fail-fast机制。 Enumerator(int type, boolean iterator) {
this.type = type;
this.iterator = iterator;
} public boolean hasMoreElements() {
Entry<?,?> e = entry;
int i = index;
Entry<?,?>[] t = table;
/* Use locals for faster loop iteration */
while (e == null && i > 0) {
e = t[--i];
}
entry = e;
index = i;
return e != null;
} @SuppressWarnings("unchecked")
public T nextElement() {
Entry<?,?> et = entry;
int i = index;
Entry<?,?>[] t = table;
/* Use locals for faster loop iteration */
while (et == null && i > 0) {
et = t[--i];
}
entry = et;
index = i;
if (et != null) {
Entry<?,?> e = lastReturned = entry;
entry = e.next;
return type == KEYS ? (T)e.key : (type == VALUES ? (T)e.value : (T)e);
}
throw new NoSuchElementException("Hashtable Enumerator");
} // Iterator methods
public boolean hasNext() {
return hasMoreElements();
} public T next() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
return nextElement();
} public void remove() {
if (!iterator)
throw new UnsupportedOperationException();
if (lastReturned == null)
throw new IllegalStateException("Hashtable Enumerator");
if (modCount != expectedModCount)
throw new ConcurrentModificationException(); synchronized(Hashtable.this) {
Entry<?,?>[] tab = Hashtable.this.table;
int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length; @SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
for(Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
if (e == lastReturned) {
modCount++;
expectedModCount++;
if (prev == null)
tab[index] = e.next;
else
prev.next = e.next;
count--;
lastReturned = null;
return;
}
}
throw new ConcurrentModificationException();
}
}
}
}

集合类

类名 实现思路
ArrayList  
LinkedList  
Vector  
HashMap  
HashTable  
LinkedHashMap  

并发包concurrent

类名 实现思路
ConcurrentHashMap  
AbstractQueuedSynchronizer  
ReentrantLock  

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