自己写一个Map

Map的实现其实很简单，一个key对应一个value就行 。

本Map是写着玩的，是想告诉初学者我们也可以写一个简单的Map来自己用

代码：

public class MyMap<K, V> {
    private Node<K, V>[] nodes;
    private int size;

    private static class Node<K, V> {
        K key;
        V value;

        Node(K key, V value) {
            this.key = key;
            this.value = value;
        }
    }

    private void put(K key, V value) {
        if (nodes == null) {
            nodes = new Node[10];
        }
        int index = indexOfKey(key);
        if (index != -1) {
            nodes[index].value = value;
        } else {
            nodes[size] = new Node<>(key, value);
            size++;
        }
    }

    private int indexOfKey(K key) {
        for (int index = 0; index < size; index++) {
            if (key.equals(this.nodes[index].key)) {
                return index;
            }
        }
        return -1;
    }

    public V get(K key) {
        int index = indexOfKey(key);
        if (index != -1) {
            return (V) nodes[index].value;
        }
        return null;
    }

    public int size() {
        return size;
    }

    public void remove(K key) {
        int index = indexOfKey(key);

        if (index != -1) {
            System.arraycopy(nodes, index + 1, nodes, index, size - 1);
            nodes[--size] = null;
        }

    }

    public void clear() {
        nodes = null;
        size = 0;
    }

    private static class Person {
        private String name;
        private Integer age;

        public Person(String name, Integer age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public Integer getAge() {
            return age;
        }

        public void setAge(Integer age) {
            this.age = age;
        }

        @Override
        public String toString() {
            return "Person{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    '}';
        }
    }

    public static void main(String[] args) {
        MyMap<String, Person> myMap = new MyMap<>();
        myMap.put("lzl", new Person("lzl", 21));
        myMap.put("zwt", new Person("zwt", 21));
        System.out.println("lzl的年龄是：" + myMap.get("lzl").getAge());
        System.out.println("zwt的年龄是：" + myMap.get("zwt").getAge());
        System.out.println("myMap的大小是：" + myMap.size());

        myMap.clear();
        System.out.println("clear myMap的大小是：" + myMap.size());

        MyMap<String, Integer> myMap1 = new MyMap<>();
        myMap1.put("zwt", 21);
        System.out.println(myMap1.get("zwt"));

    }
}

结果：

lzl的年龄是：21
zwt的年龄是：21
myMap的大小是：2
clear myMap的大小是：0
21

并没有实现Map接口 ， 没有考虑到底层数组的扩容 。