jdk1.8hashmap源码解析

/*
* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

*
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*
*/

package java.util;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;

/**
* Hash table based implementation of the <tt>Map</tt> interface. This
* implementation provides all of the optional map operations, and permits
* <tt>null</tt> values and the <tt>null</tt> key. (The <tt>HashMap</tt>
* class is roughly equivalent to <tt>Hashtable</tt>, except that it is
* unsynchronized and permits nulls.) This class makes no guarantees as to
* the order of the map; in particular, it does not guarantee that the order
* will remain constant over time.
*
* This implementation provides constant-time performance for the basic
* operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
* disperses the elements properly among the buckets. Iteration over
* collection views requires time proportional to the "capacity" of the
* <tt>HashMap</tt> instance (the number of buckets) plus its size (the number
* of key-value mappings). Thus, it's very important not to set the initial
* capacity too high (or the load factor too low) if iteration performance is
* important.
*
* An instance of <tt>HashMap</tt> has two parameters that affect its
* performance: initial capacity and load factor. The
* capacity is the number of buckets in the hash table, and the initial
* capacity is simply the capacity at the time the hash table is created. The
* load factor is a measure of how full the hash table is allowed to
* get before its capacity is automatically increased. When the number of
* entries in the hash table exceeds the product of the load factor and the
* current capacity, the hash table is rehashed (that is, internal data
* structures are rebuilt) so that the hash table has approximately twice the
* number of buckets.
*
* As a general rule, the default load factor (.75) offers a good
* tradeoff between time and space costs. Higher values decrease the
* space overhead but increase the lookup cost (reflected in most of
* the operations of the <tt>HashMap</tt> class, including
* <tt>get</tt> and <tt>put</tt>). The expected number of entries in
* the map and its load factor should be taken into account when
* setting its initial capacity, so as to minimize the number of
* rehash operations. If the initial capacity is greater than the
* maximum number of entries divided by the load factor, no rehash
* operations will ever occur.
*
* If many mappings are to be stored in a <tt>HashMap</tt>
* instance, creating it with a sufficiently large capacity will allow
* the mappings to be stored more efficiently than letting it perform
* automatic rehashing as needed to grow the table. Note that using
* many keys with the same {@code hashCode()} is a sure way to slow
* down performance of any hash table. To ameliorate impact, when keys
* are {@link Comparable}, this class may use comparison order among
* keys to help break ties.
*
* Note that this implementation is not synchronized.
* If multiple threads access a hash map concurrently, and at least one of
* the threads modifies the map structurally, it must be
* synchronized externally. (A structural modification is any operation
* that adds or deletes one or more mappings; merely changing the value
* associated with a key that an instance already contains is not a
* structural modification.) This is typically accomplished by
* synchronizing on some object that naturally encapsulates the map.
*
* If no such object exists, the map should be "wrapped" using the
* {@link Collections#synchronizedMap Collections.synchronizedMap}
* method. This is best done at creation time, to prevent accidental
* unsynchronized access to the map:<pre>
* Map m = Collections.synchronizedMap(new HashMap(...));</pre>
*
* The iterators returned by all of this class's "collection view methods"
* are fail-fast: if the map is structurally modified at any time after
* the iterator is created, in any way except through the iterator's own
* <tt>remove</tt> method, the iterator will throw a
* {@link ConcurrentModificationException}. Thus, in the face of concurrent
* modification, the iterator fails quickly and cleanly, rather than risking
* arbitrary, non-deterministic behavior at an undetermined time in the
* future.
*
* Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: the fail-fast behavior of iterators
* should be used only to detect bugs.
*
* This class is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*
* @author Doug Lea
* @author Josh Bloch
* @author Arthur van Hoff
* @author Neal Gafter
* @see Object#hashCode()
* @see Collection
* @see Map
* @see TreeMap
* @see Hashtable
* @since 1.2
*/
public class HashMap<K,V> extends AbstractMap<K,V>
 implements Map<K,V>, Cloneable, Serializable {

 private static final long serialVersionUID = 362498820763181265L;

 /*
* Implementation notes.
*
* This map usually acts as a binned (bucketed) hash table, but
* when bins get too large, they are transformed into bins of
* TreeNodes, each structured similarly to those in
* java.util.TreeMap. Most methods try to use normal bins, but
* relay to TreeNode methods when applicable (simply by checking
* instanceof a node). Bins of TreeNodes may be traversed and
* used like any others, but additionally support faster lookup
* when overpopulated. However, since the vast majority of bins in
* normal use are not overpopulated, checking for existence of
* tree bins may be delayed in the course of table methods.
*
* Tree bins (i.e., bins whose elements are all TreeNodes) are
* ordered primarily by hashCode, but in the case of ties, if two
* elements are of the same "class C implements Comparable<C>",
* type then their compareTo method is used for ordering. (We
* conservatively check generic types via reflection to validate
* this -- see method comparableClassFor). The added complexity
* of tree bins is worthwhile in providing worst-case O(log n)
* operations when keys either have distinct hashes or are
* orderable, Thus, performance degrades gracefully under
* accidental or malicious usages in which hashCode() methods
* return values that are poorly distributed, as well as those in
* which many keys share a hashCode, so long as they are also
* Comparable. (If neither of these apply, we may waste about a
* factor of two in time and space compared to taking no
* precautions. But the only known cases stem from poor user
* programming practices that are already so slow that this makes
* little difference.)
*
* Because TreeNodes are about twice the size of regular nodes, we
* use them only when bins contain enough nodes to warrant use
* (see TREEIFY_THRESHOLD). And when they become too small (due to
* removal or resizing) they are converted back to plain bins. In
* usages with well-distributed user hashCodes, tree bins are
* rarely used. Ideally, under random hashCodes, the frequency of
* nodes in bins follows a Poisson distribution
* (http://en.wikipedia.org/wiki/Poisson_distribution) with a
* parameter of about 0.5 on average for the default resizing
* threshold of 0.75, although with a large variance because of
* resizing granularity. Ignoring variance, the expected
* occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
* factorial(k)). The first values are:
*
* 0: 0.60653066
* 1: 0.30326533
* 2: 0.07581633
* 3: 0.01263606
* 4: 0.00157952
* 5: 0.00015795
* 6: 0.00001316
* 7: 0.00000094
* 8: 0.00000006
* more: less than 1 in ten million
*
* The root of a tree bin is normally its first node. However,
* sometimes (currently only upon Iterator.remove), the root might
* be elsewhere, but can be recovered following parent links
* (method TreeNode.root()).
*
* All applicable internal methods accept a hash code as an
* argument (as normally supplied from a public method), allowing
* them to call each other without recomputing user hashCodes.
* Most internal methods also accept a "tab" argument, that is
* normally the current table, but may be a new or old one when
* resizing or converting.
*
* When bin lists are treeified, split, or untreeified, we keep
* them in the same relative access/traversal order (i.e., field
* Node.next) to better preserve locality, and to slightly
* simplify handling of splits and traversals that invoke
* iterator.remove. When using comparators on insertion, to keep a
* total ordering (or as close as is required here) across
* rebalancings, we compare classes and identityHashCodes as
* tie-breakers.
*
* The use and transitions among plain vs tree modes is
* complicated by the existence of subclass LinkedHashMap. See
* below for hook methods defined to be invoked upon insertion,
* removal and access that allow LinkedHashMap internals to
* otherwise remain independent of these mechanics. (This also
* requires that a map instance be passed to some utility methods
* that may create new nodes.)
*
* The concurrent-programming-like SSA-based coding style helps
* avoid aliasing errors amid all of the twisty pointer operations.
*/

/**
* The default initial capacity - MUST be a power of two.
*/
 static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

/**
* The maximum capacity, used if a higher value is implicitly specified
* by either of the constructors with arguments.
* MUST be a power of two <= 1<<30.
*/
 static final int MAXIMUM_CAPACITY = 1 << 30;

 /**
* The load factor used when none specified in constructor.
*/
 static final float DEFAULT_LOAD_FACTOR = 0.75f;

 /**
* The bin count threshold for using a tree rather than list for a
* bin. Bins are converted to trees when adding an element to a
* bin with at least this many nodes. The value must be greater
* than 2 and should be at least 8 to mesh with assumptions in
* tree removal about conversion back to plain bins upon
* shrinkage.
*/
 static final int TREEIFY_THRESHOLD = 8;

 /**
* The bin count threshold for untreeifying a (split) bin during a
* resize operation. Should be less than TREEIFY_THRESHOLD, and at
* most 6 to mesh with shrinkage detection under removal.
*/
 static final int UNTREEIFY_THRESHOLD = 6;

 /**
* The smallest table capacity for which bins may be treeified.
* (Otherwise the table is resized if too many nodes in a bin.)
* Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
* between resizing and treeification thresholds.
*/
 static final int MIN_TREEIFY_CAPACITY = 64;

 /**
* Basic hash bin node, used for most entries. (See below for
* TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
*/
 static class Node<K,V> implements Map.Entry<K,V> {
 final int hash;
 final K key;
 V value;
Node<K,V> next;

Node(int hash, K key, V value, Node<K,V> next) {
 this.hash = hash;
 this.key = key;
 this.value = value;
 this.next = next;
}

 public final K getKey() { return key; }
 public final V getValue() { return value; }
 public final String toString() { return key + "=" + value; }

 public final int hashCode() {
 return Objects.hashCode(key) ^ Objects.hashCode(value);
}

 public final V setValue(V newValue) {
 V oldValue = value;
 value = newValue;
 return oldValue;
}

 public final boolean equals(Object o) {
 if (o == this)
 return true;
 if (o instanceof Map.Entry) {
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
 if (Objects.equals(key, e.getKey()) &&
Objects.equals(value, e.getValue()))
 return true;
}
 return false;
}
}

 /* ---------------- Static utilities -------------- */

/**
* Computes key.hashCode() and spreads (XORs) higher bits of hash
* to lower. Because the table uses power-of-two masking, sets of
* hashes that vary only in bits above the current mask will
* always collide. (Among known examples are sets of Float keys
* holding consecutive whole numbers in small tables.) So we
* apply a transform that spreads the impact of higher bits
* downward. There is a tradeoff between speed, utility, and
* quality of bit-spreading. Because many common sets of hashes
* are already reasonably distributed (so don't benefit from
* spreading), and because we use trees to handle large sets of
* collisions in bins, we just XOR some shifted bits in the
* cheapest possible way to reduce systematic lossage, as well as
* to incorporate impact of the highest bits that would otherwise
* never be used in index calculations because of table bounds.
*/
 static final int hash(Object key) {
 int h;
 return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}

 /**
* Returns x's Class if it is of the form "class C implements
* Comparable<C>", else null.
*/
 static Class<?> comparableClassFor(Object x) {
 if (x instanceof Comparable) {
Class<?> c; Type[] ts, as; Type t; ParameterizedType p;
 if ((c = x.getClass()) == String.class) // bypass checks
 return c;
 if ((ts = c.getGenericInterfaces()) != null) {
 for (int i = 0; i < ts.length; ++i) {
 if (((t = ts[i]) instanceof ParameterizedType) &&
((p = (ParameterizedType)t).getRawType() ==
Comparable.class) &&
(as = p.getActualTypeArguments()) != null &&
as.length == 1 && as[0] == c) // type arg is c
 return c;
}
}
}
 return null;
}

 /**
* Returns k.compareTo(x) if x matches kc (k's screened comparable
* class), else 0.
*/
 @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable
 static int compareComparables(Class<?> kc, Object k, Object x) {
 return (x == null || x.getClass() != kc ? 0 :
((Comparable)k).compareTo(x));
}

 /**

* Returns a power of two size for the given target capacity.

默认初始容量为16，加载因子为0.75，若给初值为21则设置的容量为32，即大于21的最小2的n次幂（16，32，64，128。。。）

*/
 static final int tableSizeFor(int cap) {
 int n = cap - 1;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
 return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
}

 /* ---------------- Fields -------------- */

/**
* The table, initialized on first use, and resized as
* necessary. When allocated, length is always a power of two.
* (We also tolerate length zero in some operations to allow
* bootstrapping mechanics that are currently not needed.)
*/
 transient Node<K,V>[] table;

 /**
* Holds cached entrySet(). Note that AbstractMap fields are used
* for keySet() and values().
*/
 transient Set<Map.Entry<K,V>> entrySet;

 /**
* The number of key-value mappings contained in this map.
*/
 transient int size;

 /**
* The number of times this HashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the HashMap or otherwise modify its internal structure (e.g.,
* rehash). This field is used to make iterators on Collection-views of
* the HashMap fail-fast. (See ConcurrentModificationException).
*/
 transient int modCount;

 /**
* The next size value at which to resize (capacity * load factor).
*
* @serial
*/
// (The javadoc description is true upon serialization.
// Additionally, if the table array has not been allocated, this
// field holds the initial array capacity, or zero signifying
// DEFAULT_INITIAL_CAPACITY.)
 int threshold;

 /**
* The load factor for the hash table.
*
* @serial
*/
 final float loadFactor;

 /* ---------------- Public operations -------------- */

/**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @throws IllegalArgumentException if the initial capacity is negative
* or the load factor is nonpositive
*/
 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;
 this.threshold = tableSizeFor(initialCapacity);
}

 /**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity the initial capacity.
* @throws IllegalArgumentException if the initial capacity is negative.
*/
 public HashMap(int initialCapacity) {
 this(initialCapacity, DEFAULT_LOAD_FACTOR);
}

 /**
* Constructs an empty <tt>HashMap</tt> with the default initial capacity
* (16) and the default load factor (0.75).
*/
 public HashMap() {
 this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
 }

 /**
* Constructs a new <tt>HashMap</tt> with the same mappings as the
* specified <tt>Map</tt>. The <tt>HashMap</tt> is created with
* default load factor (0.75) and an initial capacity sufficient to
* hold the mappings in the specified <tt>Map</tt>.
*
* @param m the map whose mappings are to be placed in this map
* @throws NullPointerException if the specified map is null
*/
 public HashMap(Map<? extends K, ? extends V> m) {
 this.loadFactor = DEFAULT_LOAD_FACTOR;
putMapEntries(m, false);
}

 /**
* Implements Map.putAll and Map constructor
*
* @param m the map
* @param evict false when initially constructing this map, else
* true (relayed to method afterNodeInsertion).
*/
 final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
 int s = m.size();
 if (s > 0) {
 if (table == null) { // pre-size
 float ft = ((float)s / loadFactor) + 1.0F;
 int t = ((ft < (float)MAXIMUM_CAPACITY) ?
(int)ft : MAXIMUM_CAPACITY);
 if (t > threshold)
 threshold = tableSizeFor(t);
}
 else if (s > threshold)
resize();
 for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
 K key = e.getKey();
 V value = e.getValue();
putVal(hash(key), key, value, false, evict);
}
}
}

 /**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map
*/
 public int size() {
 return size;
}

 /**
* Returns <tt>true</tt> if this map contains no key-value mappings.
*
* @return <tt>true</tt> if this map contains no key-value mappings
*/
 public boolean isEmpty() {
 return size == 0;
}

 /**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
*
* More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key==null ? k==null :
* key.equals(k))}, then this method returns {@code v}; otherwise
* it returns {@code null}. (There can be at most one such mapping.)
*
* A return value of {@code null} does not necessarily
* indicate that the map contains no mapping for the key; it's also
* possible that the map explicitly maps the key to {@code null}.
* The {@link #containsKey containsKey} operation may be used to
* distinguish these two cases.
*
* @see #put(Object, Object)
*/
 public V get(Object key) {
Node<K,V> e;
 return (e = getNode(hash(key), key)) == null ? null : e.value;
}

 /**
* Implements Map.get and related methods
*
* @param hash hash for key
* @param key the key
* @return the node, or null if none
*/
 final Node<K,V> getNode(int hash, Object key) {
Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
 if ((tab = table) != null && (n = tab.length) > 0 &&
(first = tab[(n - 1) & hash]) != null) {
 if (first.hash == hash && // always check first node
 ((k = first.key) == key || (key != null && key.equals(k))))
 return first;
 if ((e = first.next) != null) {
 if (first instanceof TreeNode)
 return ((TreeNode<K,V>)first).getTreeNode(hash, key);
 do {
 if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
 return e;
} while ((e = e.next) != null);
}
}
 return null;
}

 /**
* Returns <tt>true</tt> if this map contains a mapping for the
* specified key.
*
* @param key The key whose presence in this map is to be tested
* @return <tt>true</tt> if this map contains a mapping for the specified
* key.
*/
 public boolean containsKey(Object key) {
 return getNode(hash(key), key) != null;
}

 /**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for the key, the old
* value is replaced.
*
* @param key key with which the specified value is to be associated
* @param value value to be associated with the specified key
* @return the previous value associated with <tt>key</tt>, or
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
* (A <tt>null</tt> return can also indicate that the map
* previously associated <tt>null</tt> with <tt>key</tt>.)
*/
 public V put(K key, V value) {
 return putVal(hash(key), key, value, false, true);
}

 /**
* Implements Map.put and related methods
*
* @param hash hash for key
* @param key the key
* @param value the value to put
* @param onlyIfAbsent if true, don't change existing value
* @param evict if false, the table is in creation mode.
* @return previous value, or null if none
*/
 final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<K,V>[] tab; Node<K,V> p; int n, i;
 if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;
 if ((p = tab[i = (n - 1) & hash]) == null)
tab[i] = newNode(hash, key, value, null);
 else {
Node<K,V> e; K k;
 if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
e = p;
 else if (p instanceof TreeNode)
e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
 else {
 for (int binCount = 0; ; ++binCount) {
 if ((e = p.next) == null) {
p.next = newNode(hash, key, value, null);
 if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
 treeifyBin(tab, hash);
 break;
}
 if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
 break;
p = e;
}
}
 if (e != null) { // existing mapping for key
 V oldValue = e.value;
 if (!onlyIfAbsent || oldValue == null)
e.value = value;
afterNodeAccess(e);
 return oldValue;
}
}
++modCount;
 if (++size > threshold)
resize();
afterNodeInsertion(evict);
 return null;
}

 /**
* Initializes or doubles table size. If null, allocates in
* accord with initial capacity target held in field threshold.
* Otherwise, because we are using power-of-two expansion, the
* elements from each bin must either stay at same index, or move
* with a power of two offset in the new table.
*
* @return the table
*/
 final Node<K,V>[] resize() {
Node<K,V>[] oldTab = table;
 int oldCap = (oldTab == null) ? 0 : oldTab.length;
 int oldThr = threshold;
 int newCap, newThr = 0;
 if (oldCap > 0) {
 if (oldCap >= MAXIMUM_CAPACITY) {
 threshold = Integer.MAX_VALUE;
 return oldTab;
}
 else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
oldCap >= DEFAULT_INITIAL_CAPACITY)
newThr = oldThr << 1; // double threshold
 }
 else if (oldThr > 0) // initial capacity was placed in threshold
 newCap = oldThr;
 else { // zero initial threshold signifies using defaults
 newCap = DEFAULT_INITIAL_CAPACITY;
newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
}
 if (newThr == 0) {
 float ft = (float)newCap * loadFactor;
newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
(int)ft : Integer.MAX_VALUE);
}
 threshold = newThr;
 @SuppressWarnings({"rawtypes","unchecked"})
Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
 table = newTab;
 if (oldTab != null) {
 for (int j = 0; j < oldCap; ++j) {
Node<K,V> e;
 if ((e = oldTab[j]) != null) {
oldTab[j] = null;
 if (e.next == null)
newTab[e.hash & (newCap - 1)] = e;
 else if (e instanceof TreeNode)
((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
 else { // preserve order
 Node<K,V> loHead = null, loTail = null;
Node<K,V> hiHead = null, hiTail = null;
Node<K,V> next;
 do {
next = e.next;
 if ((e.hash & oldCap) == 0) {
 if (loTail == null)
loHead = e;
 else
 loTail.next = e;
loTail = e;
}
 else {
 if (hiTail == null)
hiHead = e;
 else
 hiTail.next = e;
hiTail = e;
}
} while ((e = next) != null);
 if (loTail != null) {
loTail.next = null;
newTab[j] = loHead;
}
 if (hiTail != null) {
hiTail.next = null;
newTab[j + oldCap] = hiHead;
}
}
}
}
}
 return newTab;
}

 /**
* Replaces all linked nodes in bin at index for given hash unless
* table is too small, in which case resizes instead.
*/
 final void treeifyBin(Node<K,V>[] tab, int hash) {
 int n, index; Node<K,V> e;
 if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
resize();
 else if ((e = tab[index = (n - 1) & hash]) != null) {
TreeNode<K,V> hd = null, tl = null;
 do {
TreeNode<K,V> p = replacementTreeNode(e, null);
 if (tl == null)
hd = p;
 else {
p.prev = tl;
tl.next = p;
}
tl = p;
} while ((e = e.next) != null);
 if ((tab[index] = hd) != null)
hd.treeify(tab);
}
}

 /**
* Copies all of the mappings from the specified map to this map.
* These mappings will replace any mappings that this map had for
* any of the keys currently in the specified map.
*
* @param m mappings to be stored in this map
* @throws NullPointerException if the specified map is null
*/
 public void putAll(Map<? extends K, ? extends V> m) {
putMapEntries(m, true);
}

 /**
* Removes the mapping for the specified key from this map if present.
*
* @param key key whose mapping is to be removed from the map
* @return the previous value associated with <tt>key</tt>, or
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
* (A <tt>null</tt> return can also indicate that the map
* previously associated <tt>null</tt> with <tt>key</tt>.)
*/
 public V remove(Object key) {
Node<K,V> e;
 return (e = removeNode(hash(key), key, null, false, true)) == null ?
 null : e.value;
}

 /**
* Implements Map.remove and related methods
*
* @param hash hash for key
* @param key the key
* @param value the value to match if matchValue, else ignored
* @param matchValue if true only remove if value is equal
* @param movable if false do not move other nodes while removing
* @return the node, or null if none
*/
 final Node<K,V> removeNode(int hash, Object key, Object value,
boolean matchValue, boolean movable) {
Node<K,V>[] tab; Node<K,V> p; int n, index;
 if ((tab = table) != null && (n = tab.length) > 0 &&
(p = tab[index = (n - 1) & hash]) != null) {
Node<K,V> node = null, e; K k; V v;
 if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
node = p;
 else if ((e = p.next) != null) {
 if (p instanceof TreeNode)
node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
 else {
 do {
 if (e.hash == hash &&
((k = e.key) == key ||
(key != null && key.equals(k)))) {
node = e;
 break;
}
p = e;
} while ((e = e.next) != null);
}
}
 if (node != null && (!matchValue || (v = node.value) == value ||
(value != null && value.equals(v)))) {
 if (node instanceof TreeNode)
((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
 else if (node == p)
tab[index] = node.next;
 else
 p.next = node.next;
++modCount;
--size;
afterNodeRemoval(node);
 return node;
}
}
 return null;
}

 /**
* Removes all of the mappings from this map.
* The map will be empty after this call returns.
*/
 public void clear() {
Node<K,V>[] tab;
 modCount++;
 if ((tab = table) != null && size > 0) {
 size = 0;
 for (int i = 0; i < tab.length; ++i)
tab[i] = null;
}
}

 /**
* Returns <tt>true</tt> if this map maps one or more keys to the
* specified value.
*
* @param value value whose presence in this map is to be tested
* @return <tt>true</tt> if this map maps one or more keys to the
* specified value
*/
 public boolean containsValue(Object value) {
Node<K,V>[] tab; V v;
 if ((tab = table) != null && size > 0) {
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next) {
 if ((v = e.value) == value ||
(value != null && value.equals(v)))
 return true;
}
}
}
 return false;
}

 /**
* Returns a {@link Set} view of the keys contained in this map.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. If the map is modified
* while an iteration over the set is in progress (except through
* the iterator's own <tt>remove</tt> operation), the results of
* the iteration are undefined. The set supports element removal,
* which removes the corresponding mapping from the map, via the
* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
* operations.
*
* @return a set view of the keys contained in this map
*/
 public Set<K> keySet() {
Set<K> ks = keySet;
 if (ks == null) {
ks = new KeySet();
 keySet = ks;
}
 return ks;
}

 final class KeySet extends AbstractSet<K> {
 public final int size() { return size; }
 public final void clear() { HashMap.this.clear(); }
 public final Iterator<K> iterator() { return new KeyIterator(); }
 public final boolean contains(Object o) { return containsKey(o); }
 public final boolean remove(Object key) {
 return removeNode(hash(key), key, null, false, true) != null;
}
 public final Spliterator<K> spliterator() {
 return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
}
 public final void forEach(Consumer<? super K> action) {
Node<K,V>[] tab;
 if (action == null)
 throw new NullPointerException();
 if (size > 0 && (tab = table) != null) {
 int mc = modCount;
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e.key);
}
 if (modCount != mc)
 throw new ConcurrentModificationException();
}
}
}

 /**
* Returns a {@link Collection} view of the values contained in this map.
* The collection is backed by the map, so changes to the map are
* reflected in the collection, and vice-versa. If the map is
* modified while an iteration over the collection is in progress
* (except through the iterator's own <tt>remove</tt> operation),
* the results of the iteration are undefined. The collection
* supports element removal, which removes the corresponding
* mapping from the map, via the <tt>Iterator.remove</tt>,
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
* support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a view of the values contained in this map
*/
 public Collection<V> values() {
Collection<V> vs = values;
 if (vs == null) {
vs = new Values();
 values = vs;
}
 return vs;
}

 final class Values extends AbstractCollection<V> {
 public final int size() { return size; }
 public final void clear() { HashMap.this.clear(); }
 public final Iterator<V> iterator() { return new ValueIterator(); }
 public final boolean contains(Object o) { return containsValue(o); }
 public final Spliterator<V> spliterator() {
 return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
}
 public final void forEach(Consumer<? super V> action) {
Node<K,V>[] tab;
 if (action == null)
 throw new NullPointerException();
 if (size > 0 && (tab = table) != null) {
 int mc = modCount;
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e.value);
}
 if (modCount != mc)
 throw new ConcurrentModificationException();
}
}
}

 /**
* Returns a {@link Set} view of the mappings contained in this map.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. If the map is modified
* while an iteration over the set is in progress (except through
* the iterator's own <tt>remove</tt> operation, or through the
* <tt>setValue</tt> operation on a map entry returned by the
* iterator) the results of the iteration are undefined. The set
* supports element removal, which removes the corresponding
* mapping from the map, via the <tt>Iterator.remove</tt>,
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
* <tt>clear</tt> operations. It does not support the
* <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a set view of the mappings contained in this map
*/
 public Set<Map.Entry<K,V>> entrySet() {
Set<Map.Entry<K,V>> es;
 return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
}

 final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
 public final int size() { return size; }
 public final void clear() { HashMap.this.clear(); }
 public final Iterator<Map.Entry<K,V>> iterator() {
 return new EntryIterator();
}
 public final boolean contains(Object o) {
 if (!(o instanceof Map.Entry))
 return false;
Map.Entry<?,?> e = (Map.Entry<?,?>) o;
Object key = e.getKey();
Node<K,V> candidate = getNode(hash(key), key);
 return candidate != null && candidate.equals(e);
}
 public final boolean remove(Object o) {
 if (o instanceof Map.Entry) {
Map.Entry<?,?> e = (Map.Entry<?,?>) o;
Object key = e.getKey();
Object value = e.getValue();
 return removeNode(hash(key), key, value, true, true) != null;
}
 return false;
}
 public final Spliterator<Map.Entry<K,V>> spliterator() {
 return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
}
 public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
Node<K,V>[] tab;
 if (action == null)
 throw new NullPointerException();
 if (size > 0 && (tab = table) != null) {
 int mc = modCount;
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e);
}
 if (modCount != mc)
 throw new ConcurrentModificationException();
}
}
}

 // Overrides of JDK8 Map extension methods

 @Override
 public V getOrDefault(Object key, V defaultValue) {
Node<K,V> e;
 return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
}

 @Override
 public V putIfAbsent(K key, V value) {
 return putVal(hash(key), key, value, true, true);
}

 @Override
 public boolean remove(Object key, Object value) {
 return removeNode(hash(key), key, value, true, true) != null;
}

 @Override
 public boolean replace(K key, V oldValue, V newValue) {
Node<K,V> e; V v;
 if ((e = getNode(hash(key), key)) != null &&
((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
e.value = newValue;
afterNodeAccess(e);
 return true;
}
 return false;
}

 @Override
 public V replace(K key, V value) {
Node<K,V> e;
 if ((e = getNode(hash(key), key)) != null) {
 V oldValue = e.value;
e.value = value;
afterNodeAccess(e);
 return oldValue;
}
 return null;
}

 @Override
 public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
 if (mappingFunction == null)
 throw new NullPointerException();
 int hash = hash(key);
Node<K,V>[] tab; Node<K,V> first; int n, i;
 int binCount = 0;
TreeNode<K,V> t = null;
Node<K,V> old = null;
 if (size > threshold || (tab = table) == null ||
(n = tab.length) == 0)
n = (tab = resize()).length;
 if ((first = tab[i = (n - 1) & hash]) != null) {
 if (first instanceof TreeNode)
old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
 else {
Node<K,V> e = first; K k;
 do {
 if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
old = e;
 break;
}
++binCount;
} while ((e = e.next) != null);
}
 V oldValue;
 if (old != null && (oldValue = old.value) != null) {
afterNodeAccess(old);
 return oldValue;
}
}
 V v = mappingFunction.apply(key);
 if (v == null) {
 return null;
} else if (old != null) {
old.value = v;
afterNodeAccess(old);
 return v;
}
 else if (t != null)
t.putTreeVal(this, tab, hash, key, v);
 else {
tab[i] = newNode(hash, key, v, first);
 if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
}
++modCount;
++size;
afterNodeInsertion(true);
 return v;
}

 public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
 if (remappingFunction == null)
 throw new NullPointerException();
Node<K,V> e; V oldValue;
 int hash = hash(key);
 if ((e = getNode(hash, key)) != null &&
(oldValue = e.value) != null) {
 V v = remappingFunction.apply(key, oldValue);
 if (v != null) {
e.value = v;
afterNodeAccess(e);
 return v;
}
 else
 removeNode(hash, key, null, false, true);
}
 return null;
}

 @Override
 public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
 if (remappingFunction == null)
 throw new NullPointerException();
 int hash = hash(key);
Node<K,V>[] tab; Node<K,V> first; int n, i;
 int binCount = 0;
TreeNode<K,V> t = null;
Node<K,V> old = null;
 if (size > threshold || (tab = table) == null ||
(n = tab.length) == 0)
n = (tab = resize()).length;
 if ((first = tab[i = (n - 1) & hash]) != null) {
 if (first instanceof TreeNode)
old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
 else {
Node<K,V> e = first; K k;
 do {
 if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
old = e;
 break;
}
++binCount;
} while ((e = e.next) != null);
}
}
 V oldValue = (old == null) ? null : old.value;
 V v = remappingFunction.apply(key, oldValue);
 if (old != null) {
 if (v != null) {
old.value = v;
afterNodeAccess(old);
}
 else
 removeNode(hash, key, null, false, true);
}
 else if (v != null) {
 if (t != null)
t.putTreeVal(this, tab, hash, key, v);
 else {
tab[i] = newNode(hash, key, v, first);
 if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
}
++modCount;
++size;
afterNodeInsertion(true);
}
 return v;
}

 @Override
 public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
 if (value == null)
 throw new NullPointerException();
 if (remappingFunction == null)
 throw new NullPointerException();
 int hash = hash(key);
Node<K,V>[] tab; Node<K,V> first; int n, i;
 int binCount = 0;
TreeNode<K,V> t = null;
Node<K,V> old = null;
 if (size > threshold || (tab = table) == null ||
(n = tab.length) == 0)
n = (tab = resize()).length;
 if ((first = tab[i = (n - 1) & hash]) != null) {
 if (first instanceof TreeNode)
old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
 else {
Node<K,V> e = first; K k;
 do {
 if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
old = e;
 break;
}
++binCount;
} while ((e = e.next) != null);
}
}
 if (old != null) {
 V v;
 if (old.value != null)
v = remappingFunction.apply(old.value, value);
 else
 v = value;
 if (v != null) {
old.value = v;
afterNodeAccess(old);
}
 else
 removeNode(hash, key, null, false, true);
 return v;
}
 if (value != null) {
 if (t != null)
t.putTreeVal(this, tab, hash, key, value);
 else {
tab[i] = newNode(hash, key, value, first);
 if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
}
++modCount;
++size;
afterNodeInsertion(true);
}
 return value;
}

 @Override
 public void forEach(BiConsumer<? super K, ? super V> action) {
Node<K,V>[] tab;
 if (action == null)
 throw new NullPointerException();
 if (size > 0 && (tab = table) != null) {
 int mc = modCount;
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e.key, e.value);
}
 if (modCount != mc)
 throw new ConcurrentModificationException();
}
}

 @Override
 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
Node<K,V>[] tab;
 if (function == null)
 throw new NullPointerException();
 if (size > 0 && (tab = table) != null) {
 int mc = modCount;
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next) {
e.value = function.apply(e.key, e.value);
}
}
 if (modCount != mc)
 throw new ConcurrentModificationException();
}
}

 /* ------------------------------------------------------------ */
// Cloning and serialization

/**
* Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
* values themselves are not cloned.
*
* @return a shallow copy of this map
*/
 @SuppressWarnings("unchecked")
 @Override
 public Object clone() {
HashMap<K,V> result;
 try {
result = (HashMap<K,V>)super.clone();
} catch (CloneNotSupportedException e) {
 // this shouldn't happen, since we are Cloneable
 throw new InternalError(e);
}
result.reinitialize();
result.putMapEntries(this, false);
 return result;
}

 // These methods are also used when serializing HashSets
 final float loadFactor() { return loadFactor; }
 final int capacity() {
 return (table != null) ? table.length :
(threshold > 0) ? threshold :
 DEFAULT_INITIAL_CAPACITY;
}

 /**
* Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
* serialize it).
*
* @serialData The capacity of the HashMap (the length of the
* bucket array) is emitted (int), followed by the
* size (an int, the number of key-value
* mappings), followed by the key (Object) and value (Object)
* for each key-value mapping. The key-value mappings are
* emitted in no particular order.
*/
 private void writeObject(java.io.ObjectOutputStream s)
 throws IOException {
 int buckets = capacity();
 // Write out the threshold, loadfactor, and any hidden stuff
 s.defaultWriteObject();
s.writeInt(buckets);
s.writeInt(size);
internalWriteEntries(s);
}

 /**
* Reconstitute the {@code HashMap} instance from a stream (i.e.,
* deserialize it).
*/
 private void readObject(java.io.ObjectInputStream s)
 throws IOException, ClassNotFoundException {
 // Read in the threshold (ignored), loadfactor, and any hidden stuff
 s.defaultReadObject();
reinitialize();
 if (loadFactor <= 0 || Float.isNaN(loadFactor))
 throw new InvalidObjectException("Illegal load factor: " +
loadFactor);
s.readInt(); // Read and ignore number of buckets
 int mappings = s.readInt(); // Read number of mappings (size)
 if (mappings < 0)
 throw new InvalidObjectException("Illegal mappings count: " +
mappings);
 else if (mappings > 0) { // (if zero, use defaults)
// Size the table using given load factor only if within
// range of 0.25...4.0
 float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
 float fc = (float)mappings / lf + 1.0f;
 int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
DEFAULT_INITIAL_CAPACITY :
(fc >= MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY :
tableSizeFor((int)fc));
 float ft = (float)cap * lf;
 threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
(int)ft : Integer.MAX_VALUE);
 @SuppressWarnings({"rawtypes","unchecked"})
Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
 table = tab;

 // Read the keys and values, and put the mappings in the HashMap
 for (int i = 0; i < mappings; i++) {
 @SuppressWarnings("unchecked")
 K key = (K) s.readObject();
 @SuppressWarnings("unchecked")
 V value = (V) s.readObject();
putVal(hash(key), key, value, false, false);
}
}
}

 /* ------------------------------------------------------------ */
// iterators

 abstract class HashIterator {
Node<K,V> next; // next entry to return
 Node<K,V> current; // current entry
 int expectedModCount; // for fast-fail
 int index; // current slot

 HashIterator() {
 expectedModCount = modCount;
Node<K,V>[] t = table;
 current = next = null;
 index = 0;
 if (t != null && size > 0) { // advance to first entry
 do {} while (index < t.length && (next = t[index++]) == null);
}
}

 public final boolean hasNext() {
 return next != null;
}

 final Node<K,V> nextNode() {
Node<K,V>[] t;
Node<K,V> e = next;
 if (modCount != expectedModCount)
 throw new ConcurrentModificationException();
 if (e == null)
 throw new NoSuchElementException();
 if ((next = (current = e).next) == null && (t = table) != null) {
 do {} while (index < t.length && (next = t[index++]) == null);
}
 return e;
}

 public final void remove() {
Node<K,V> p = current;
 if (p == null)
 throw new IllegalStateException();
 if (modCount != expectedModCount)
 throw new ConcurrentModificationException();
 current = null;
 K key = p.key;
removeNode(hash(key), key, null, false, false);
 expectedModCount = modCount;
}
}

 final class KeyIterator extends HashIterator
 implements Iterator<K> {
 public final K next() { return nextNode().key; }
}

 final class ValueIterator extends HashIterator
 implements Iterator<V> {
 public final V next() { return nextNode().value; }
}

 final class EntryIterator extends HashIterator
 implements Iterator<Map.Entry<K,V>> {
 public final Map.Entry<K,V> next() { return nextNode(); }
}

 /* ------------------------------------------------------------ */
// spliterators

 static class HashMapSpliterator<K,V> {
 final HashMap<K,V> map;
Node<K,V> current; // current node
 int index; // current index, modified on advance/split
 int fence; // one past last index
 int est; // size estimate
 int expectedModCount; // for comodification checks

 HashMapSpliterator(HashMap<K,V> m, int origin,
int fence, int est,
int expectedModCount) {
 this.map = m;
 this.index = origin;
 this.fence = fence;
 this.est = est;
 this.expectedModCount = expectedModCount;
}

 final int getFence() { // initialize fence and size on first use
 int hi;
 if ((hi = fence) < 0) {
HashMap<K,V> m = map;
 est = m.size;
 expectedModCount = m.modCount;
Node<K,V>[] tab = m.table;
hi = fence = (tab == null) ? 0 : tab.length;
}
 return hi;
}

 public final long estimateSize() {
getFence(); // force init
 return (long) est;
}
}

 static final class KeySpliterator<K,V>
 extends HashMapSpliterator<K,V>
 implements Spliterator<K> {
KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
int expectedModCount) {
 super(m, origin, fence, est, expectedModCount);
}

 public KeySpliterator<K,V> trySplit() {
 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
 return (lo >= mid || current != null) ? null :
 new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
 expectedModCount);
}

 public void forEachRemaining(Consumer<? super K> action) {
 int i, hi, mc;
 if (action == null)
 throw new NullPointerException();
HashMap<K,V> m = map;
Node<K,V>[] tab = m.table;
 if ((hi = fence) < 0) {
mc = expectedModCount = m.modCount;
hi = fence = (tab == null) ? 0 : tab.length;
}
 else
 mc = expectedModCount;
 if (tab != null && tab.length >= hi &&
(i = index) >= 0 && (i < (index = hi) || current != null)) {
Node<K,V> p = current;
 current = null;
 do {
 if (p == null)
p = tab[i++];
 else {
action.accept(p.key);
p = p.next;
}
} while (p != null || i < hi);
 if (m.modCount != mc)
 throw new ConcurrentModificationException();
}
}

 public boolean tryAdvance(Consumer<? super K> action) {
 int hi;
 if (action == null)
 throw new NullPointerException();
Node<K,V>[] tab = map.table;
 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
 while (current != null || index < hi) {
 if (current == null)
 current = tab[index++];
 else {
 K k = current.key;
 current = current.next;
action.accept(k);
 if (map.modCount != expectedModCount)
 throw new ConcurrentModificationException();
 return true;
}
}
}
 return false;
}

 public int characteristics() {
 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
Spliterator.DISTINCT;
}
}

 static final class ValueSpliterator<K,V>
 extends HashMapSpliterator<K,V>
 implements Spliterator<V> {
ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
int expectedModCount) {
 super(m, origin, fence, est, expectedModCount);
}

 public ValueSpliterator<K,V> trySplit() {
 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
 return (lo >= mid || current != null) ? null :
 new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
 expectedModCount);
}

 public void forEachRemaining(Consumer<? super V> action) {
 int i, hi, mc;
 if (action == null)
 throw new NullPointerException();
HashMap<K,V> m = map;
Node<K,V>[] tab = m.table;
 if ((hi = fence) < 0) {
mc = expectedModCount = m.modCount;
hi = fence = (tab == null) ? 0 : tab.length;
}
 else
 mc = expectedModCount;
 if (tab != null && tab.length >= hi &&
(i = index) >= 0 && (i < (index = hi) || current != null)) {
Node<K,V> p = current;
 current = null;
 do {
 if (p == null)
p = tab[i++];
 else {
action.accept(p.value);
p = p.next;
}
} while (p != null || i < hi);
 if (m.modCount != mc)
 throw new ConcurrentModificationException();
}
}

 public boolean tryAdvance(Consumer<? super V> action) {
 int hi;
 if (action == null)
 throw new NullPointerException();
Node<K,V>[] tab = map.table;
 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
 while (current != null || index < hi) {
 if (current == null)
 current = tab[index++];
 else {
 V v = current.value;
 current = current.next;
action.accept(v);
 if (map.modCount != expectedModCount)
 throw new ConcurrentModificationException();
 return true;
}
}
}
 return false;
}

 public int characteristics() {
 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
}
}

 static final class EntrySpliterator<K,V>
 extends HashMapSpliterator<K,V>
 implements Spliterator<Map.Entry<K,V>> {
EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
int expectedModCount) {
 super(m, origin, fence, est, expectedModCount);
}

 public EntrySpliterator<K,V> trySplit() {
 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
 return (lo >= mid || current != null) ? null :
 new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
 expectedModCount);
}

 public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
 int i, hi, mc;
 if (action == null)
 throw new NullPointerException();
HashMap<K,V> m = map;
Node<K,V>[] tab = m.table;
 if ((hi = fence) < 0) {
mc = expectedModCount = m.modCount;
hi = fence = (tab == null) ? 0 : tab.length;
}
 else
 mc = expectedModCount;
 if (tab != null && tab.length >= hi &&
(i = index) >= 0 && (i < (index = hi) || current != null)) {
Node<K,V> p = current;
 current = null;
 do {
 if (p == null)
p = tab[i++];
 else {
action.accept(p);
p = p.next;
}
} while (p != null || i < hi);
 if (m.modCount != mc)
 throw new ConcurrentModificationException();
}
}

 public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
 int hi;
 if (action == null)
 throw new NullPointerException();
Node<K,V>[] tab = map.table;
 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
 while (current != null || index < hi) {
 if (current == null)
 current = tab[index++];
 else {
Node<K,V> e = current;
 current = current.next;
action.accept(e);
 if (map.modCount != expectedModCount)
 throw new ConcurrentModificationException();
 return true;
}
}
}
 return false;
}

 public int characteristics() {
 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
Spliterator.DISTINCT;
}
}

 /* ------------------------------------------------------------ */
// LinkedHashMap support

/*
* The following package-protected methods are designed to be
* overridden by LinkedHashMap, but not by any other subclass.
* Nearly all other internal methods are also package-protected
* but are declared final, so can be used by LinkedHashMap, view
* classes, and HashSet.
*/

// Create a regular (non-tree) node
 Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
 return new Node<>(hash, key, value, next);
}

 // For conversion from TreeNodes to plain nodes
 Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
 return new Node<>(p.hash, p.key, p.value, next);
}

 // Create a tree bin node
 TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
 return new TreeNode<>(hash, key, value, next);
}

 // For treeifyBin
 TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
 return new TreeNode<>(p.hash, p.key, p.value, next);
}

 /**
* Reset to initial default state. Called by clone and readObject.
*/
 void reinitialize() {
 table = null;
 entrySet = null;
 keySet = null;
 values = null;
 modCount = 0;
 threshold = 0;
 size = 0;
}

 // Callbacks to allow LinkedHashMap post-actions
 void afterNodeAccess(Node<K,V> p) { }
 void afterNodeInsertion(boolean evict) { }
 void afterNodeRemoval(Node<K,V> p) { }

 // Called only from writeObject, to ensure compatible ordering.
 void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
Node<K,V>[] tab;
 if (size > 0 && (tab = table) != null) {
 for (int i = 0; i < tab.length; ++i) {
 for (Node<K,V> e = tab[i]; e != null; e = e.next) {
s.writeObject(e.key);
s.writeObject(e.value);
}
}
}
}

 /* ------------------------------------------------------------ */
// Tree bins

/**
* Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
* extends Node) so can be used as extension of either regular or
* linked node.
*/
 static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
TreeNode<K,V> parent; // red-black tree links
 TreeNode<K,V> left;
TreeNode<K,V> right;
TreeNode<K,V> prev; // needed to unlink next upon deletion
 boolean red;
TreeNode(int hash, K key, V val, Node<K,V> next) {
 super(hash, key, val, next);
}

 /**
* Returns root of tree containing this node.
*/
 final TreeNode<K,V> root() {
 for (TreeNode<K,V> r = this, p;;) {
 if ((p = r.parent) == null)
 return r;
r = p;
}
}

 /**
* Ensures that the given root is the first node of its bin.
*/
 static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
 int n;
 if (root != null && tab != null && (n = tab.length) > 0) {
 int index = (n - 1) & root.hash;
TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
 if (root != first) {
Node<K,V> rn;
tab[index] = root;
TreeNode<K,V> rp = root.prev;
 if ((rn = root.next) != null)
((TreeNode<K,V>)rn).prev = rp;
 if (rp != null)
rp.next = rn;
 if (first != null)
first.prev = root;
root.next = first;
root.prev = null;
}
 assert checkInvariants(root);
}
}

 /**
* Finds the node starting at root p with the given hash and key.
* The kc argument caches comparableClassFor(key) upon first use
* comparing keys.
*/
 final TreeNode<K,V> find(int h, Object k, Class<?> kc) {
TreeNode<K,V> p = this;
 do {
 int ph, dir; K pk;
TreeNode<K,V> pl = p.left, pr = p.right, q;
 if ((ph = p.hash) > h)
p = pl;
 else if (ph < h)
p = pr;
 else if ((pk = p.key) == k || (k != null && k.equals(pk)))
 return p;
 else if (pl == null)
p = pr;
 else if (pr == null)
p = pl;
 else if ((kc != null ||
(kc = comparableClassFor(k)) != null) &&
(dir = compareComparables(kc, k, pk)) != 0)
p = (dir < 0) ? pl : pr;
 else if ((q = pr.find(h, k, kc)) != null)
 return q;
 else
 p = pl;
} while (p != null);
 return null;
}

 /**
* Calls find for root node.
*/
 final TreeNode<K,V> getTreeNode(int h, Object k) {
 return ((parent != null) ? root() : this).find(h, k, null);
}

 /**
* Tie-breaking utility for ordering insertions when equal
* hashCodes and non-comparable. We don't require a total
* order, just a consistent insertion rule to maintain
* equivalence across rebalancings. Tie-breaking further than
* necessary simplifies testing a bit.
*/
 static int tieBreakOrder(Object a, Object b) {
 int d;
 if (a == null || b == null ||
(d = a.getClass().getName().
compareTo(b.getClass().getName())) == 0)
d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
-1 : 1);
 return d;
}

 /**
* Forms tree of the nodes linked from this node.
* @return root of tree
*/
 final void treeify(Node<K,V>[] tab) {
TreeNode<K,V> root = null;
 for (TreeNode<K,V> x = this, next; x != null; x = next) {
next = (TreeNode<K,V>)x.next;
x.left = x.right = null;
 if (root == null) {
x.parent = null;
x.red = false;
root = x;
}
 else {
 K k = x.key;
 int h = x.hash;
Class<?> kc = null;
 for (TreeNode<K,V> p = root;;) {
 int dir, ph;
 K pk = p.key;
 if ((ph = p.hash) > h)
dir = -1;
 else if (ph < h)
dir = 1;
 else if ((kc == null &&
(kc = comparableClassFor(k)) == null) ||
(dir = compareComparables(kc, k, pk)) == 0)
dir = tieBreakOrder(k, pk);

TreeNode<K,V> xp = p;
 if ((p = (dir <= 0) ? p.left : p.right) == null) {
x.parent = xp;
 if (dir <= 0)
xp.left = x;
 else
 xp.right = x;
root = balanceInsertion(root, x);
 break;
}
}
}
}
 moveRootToFront(tab, root);
}

 /**
* Returns a list of non-TreeNodes replacing those linked from
* this node.
*/
 final Node<K,V> untreeify(HashMap<K,V> map) {
Node<K,V> hd = null, tl = null;
 for (Node<K,V> q = this; q != null; q = q.next) {
Node<K,V> p = map.replacementNode(q, null);
 if (tl == null)
hd = p;
 else
 tl.next = p;
tl = p;
}
 return hd;
}

 /**
* Tree version of putVal.
*/
 final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
int h, K k, V v) {
Class<?> kc = null;
 boolean searched = false;
TreeNode<K,V> root = (parent != null) ? root() : this;
 for (TreeNode<K,V> p = root;;) {
 int dir, ph; K pk;
 if ((ph = p.hash) > h)
dir = -1;
 else if (ph < h)
dir = 1;
 else if ((pk = p.key) == k || (k != null && k.equals(pk)))
 return p;
 else if ((kc == null &&
(kc = comparableClassFor(k)) == null) ||
(dir = compareComparables(kc, k, pk)) == 0) {
 if (!searched) {
TreeNode<K,V> q, ch;
searched = true;
 if (((ch = p.left) != null &&
(q = ch.find(h, k, kc)) != null) ||
((ch = p.right) != null &&
(q = ch.find(h, k, kc)) != null))
 return q;
}
dir = tieBreakOrder(k, pk);
}

TreeNode<K,V> xp = p;
 if ((p = (dir <= 0) ? p.left : p.right) == null) {
Node<K,V> xpn = xp.next;
TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
 if (dir <= 0)
xp.left = x;
 else
 xp.right = x;
xp.next = x;
x.parent = x.prev = xp;
 if (xpn != null)
((TreeNode<K,V>)xpn).prev = x;
 moveRootToFront(tab, balanceInsertion(root, x));
 return null;
}
}
}

 /**
* Removes the given node, that must be present before this call.
* This is messier than typical red-black deletion code because we
* cannot swap the contents of an interior node with a leaf
* successor that is pinned by "next" pointers that are accessible
* independently during traversal. So instead we swap the tree
* linkages. If the current tree appears to have too few nodes,
* the bin is converted back to a plain bin. (The test triggers
* somewhere between 2 and 6 nodes, depending on tree structure).
*/
 final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
 boolean movable) {
 int n;
 if (tab == null || (n = tab.length) == 0)
 return;
 int index = (n - 1) & hash;
TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
TreeNode<K,V> succ = (TreeNode<K,V>)next, pred = prev;
 if (pred == null)
tab[index] = first = succ;
 else
 pred.next = succ;
 if (succ != null)
succ.prev = pred;
 if (first == null)
 return;
 if (root.parent != null)
root = root.root();
 if (root == null || root.right == null ||
(rl = root.left) == null || rl.left == null) {
tab[index] = first.untreeify(map); // too small
 return;
}
TreeNode<K,V> p = this, pl = left, pr = right, replacement;
 if (pl != null && pr != null) {
TreeNode<K,V> s = pr, sl;
 while ((sl = s.left) != null) // find successor
 s = sl;
 boolean c = s.red; s.red = p.red; p.red = c; // swap colors
 TreeNode<K,V> sr = s.right;
TreeNode<K,V> pp = p.parent;
 if (s == pr) { // p was s's direct parent
 p.parent = s;
s.right = p;
}
 else {
TreeNode<K,V> sp = s.parent;
 if ((p.parent = sp) != null) {
 if (s == sp.left)
sp.left = p;
 else
 sp.right = p;
}
 if ((s.right = pr) != null)
pr.parent = s;
}
p.left = null;
 if ((p.right = sr) != null)
sr.parent = p;
 if ((s.left = pl) != null)
pl.parent = s;
 if ((s.parent = pp) == null)
root = s;
 else if (p == pp.left)
pp.left = s;
 else
 pp.right = s;
 if (sr != null)
replacement = sr;
 else
 replacement = p;
}
 else if (pl != null)
replacement = pl;
 else if (pr != null)
replacement = pr;
 else
 replacement = p;
 if (replacement != p) {
TreeNode<K,V> pp = replacement.parent = p.parent;
 if (pp == null)
root = replacement;
 else if (p == pp.left)
pp.left = replacement;
 else
 pp.right = replacement;
p.left = p.right = p.parent = null;
}

TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);

 if (replacement == p) { // detach
 TreeNode<K,V> pp = p.parent;
p.parent = null;
 if (pp != null) {
 if (p == pp.left)
pp.left = null;
 else if (p == pp.right)
pp.right = null;
}
}
 if (movable)
 moveRootToFront(tab, r);
}

 /**
* Splits nodes in a tree bin into lower and upper tree bins,
* or untreeifies if now too small. Called only from resize;
* see above discussion about split bits and indices.
*
* @param map the map
* @param tab the table for recording bin heads
* @param index the index of the table being split
* @param bit the bit of hash to split on
*/
 final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
TreeNode<K,V> b = this;
 // Relink into lo and hi lists, preserving order
 TreeNode<K,V> loHead = null, loTail = null;
TreeNode<K,V> hiHead = null, hiTail = null;
 int lc = 0, hc = 0;
 for (TreeNode<K,V> e = b, next; e != null; e = next) {
next = (TreeNode<K,V>)e.next;
e.next = null;
 if ((e.hash & bit) == 0) {
 if ((e.prev = loTail) == null)
loHead = e;
 else
 loTail.next = e;
loTail = e;
++lc;
}
 else {
 if ((e.prev = hiTail) == null)
hiHead = e;
 else
 hiTail.next = e;
hiTail = e;
++hc;
}
}

 if (loHead != null) {
 if (lc <= UNTREEIFY_THRESHOLD)
tab[index] = loHead.untreeify(map);
 else {
tab[index] = loHead;
 if (hiHead != null) // (else is already treeified)
 loHead.treeify(tab);
}
}
 if (hiHead != null) {
 if (hc <= UNTREEIFY_THRESHOLD)
tab[index + bit] = hiHead.untreeify(map);
 else {
tab[index + bit] = hiHead;
 if (loHead != null)
hiHead.treeify(tab);
}
}
}

 /* ------------------------------------------------------------ */
// Red-black tree methods, all adapted from CLR

 static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
TreeNode<K,V> p) {
TreeNode<K,V> r, pp, rl;
 if (p != null && (r = p.right) != null) {
 if ((rl = p.right = r.left) != null)
rl.parent = p;
 if ((pp = r.parent = p.parent) == null)
(root = r).red = false;
 else if (pp.left == p)
pp.left = r;
 else
 pp.right = r;
r.left = p;
p.parent = r;
}
 return root;
}

 static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
TreeNode<K,V> p) {
TreeNode<K,V> l, pp, lr;
 if (p != null && (l = p.left) != null) {
 if ((lr = p.left = l.right) != null)
lr.parent = p;
 if ((pp = l.parent = p.parent) == null)
(root = l).red = false;
 else if (pp.right == p)
pp.right = l;
 else
 pp.left = l;
l.right = p;
p.parent = l;
}
 return root;
}

 static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
TreeNode<K,V> x) {
x.red = true;
 for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {
 if ((xp = x.parent) == null) {
x.red = false;
 return x;
}
 else if (!xp.red || (xpp = xp.parent) == null)
 return root;
 if (xp == (xppl = xpp.left)) {
 if ((xppr = xpp.right) != null && xppr.red) {
xppr.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
 else {
 if (x == xp.right) {
root = rotateLeft(root, x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
 if (xp != null) {
xp.red = false;
 if (xpp != null) {
xpp.red = true;
root = rotateRight(root, xpp);
}
}
}
}
 else {
 if (xppl != null && xppl.red) {
xppl.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
 else {
 if (x == xp.left) {
root = rotateRight(root, x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
 if (xp != null) {
xp.red = false;
 if (xpp != null) {
xpp.red = true;
root = rotateLeft(root, xpp);
}
}
}
}
}
}

 static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
TreeNode<K,V> x) {
 for (TreeNode<K,V> xp, xpl, xpr;;) {
 if (x == null || x == root)
 return root;
 else if ((xp = x.parent) == null) {
x.red = false;
 return x;
}
 else if (x.red) {
x.red = false;
 return root;
}
 else if ((xpl = xp.left) == x) {
 if ((xpr = xp.right) != null && xpr.red) {
xpr.red = false;
xp.red = true;
root = rotateLeft(root, xp);
xpr = (xp = x.parent) == null ? null : xp.right;
}
 if (xpr == null)
x = xp;
 else {
TreeNode<K,V> sl = xpr.left, sr = xpr.right;
 if ((sr == null || !sr.red) &&
(sl == null || !sl.red)) {
xpr.red = true;
x = xp;
}
 else {
 if (sr == null || !sr.red) {
 if (sl != null)
sl.red = false;
xpr.red = true;
root = rotateRight(root, xpr);
xpr = (xp = x.parent) == null ?
 null : xp.right;
}
 if (xpr != null) {
xpr.red = (xp == null) ? false : xp.red;
 if ((sr = xpr.right) != null)
sr.red = false;
}
 if (xp != null) {
xp.red = false;
root = rotateLeft(root, xp);
}
x = root;
}
}
}
 else { // symmetric
 if (xpl != null && xpl.red) {
xpl.red = false;
xp.red = true;
root = rotateRight(root, xp);
xpl = (xp = x.parent) == null ? null : xp.left;
}
 if (xpl == null)
x = xp;
 else {
TreeNode<K,V> sl = xpl.left, sr = xpl.right;
 if ((sl == null || !sl.red) &&
(sr == null || !sr.red)) {
xpl.red = true;
x = xp;
}
 else {
 if (sl == null || !sl.red) {
 if (sr != null)
sr.red = false;
xpl.red = true;
root = rotateLeft(root, xpl);
xpl = (xp = x.parent) == null ?
 null : xp.left;
}
 if (xpl != null) {
xpl.red = (xp == null) ? false : xp.red;
 if ((sl = xpl.left) != null)
sl.red = false;
}
 if (xp != null) {
xp.red = false;
root = rotateRight(root, xp);
}
x = root;
}
}
}
}
}

 /**
* Recursive invariant check
*/
 static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
tb = t.prev, tn = (TreeNode<K,V>)t.next;
 if (tb != null && tb.next != t)
 return false;
 if (tn != null && tn.prev != t)
 return false;
 if (tp != null && t != tp.left && t != tp.right)
 return false;
 if (tl != null && (tl.parent != t || tl.hash > t.hash))
 return false;
 if (tr != null && (tr.parent != t || tr.hash < t.hash))
 return false;
 if (t.red && tl != null && tl.red && tr != null && tr.red)
 return false;
 if (tl != null && !checkInvariants(tl))
 return false;
 if (tr != null && !checkInvariants(tr))
 return false;
 return true;
}
}

}

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