手写一个HashMap

手写一个HashMap

根据JDK中HashMap的实现原理，手写一个类似的HashMap.

代码

public class MyHashMap <K, V> {
    private int capacity;
    private Node<K, V>[] table;

    public MyHashMap () {
        this.capacity = 16;
        this.table = new Node[capacity];
    }

    public MyHashMap (int capacity) {
        this.capacity = capacity;
        this.table = new Node[capacity];
    }

    public void put(K key, V value) {
        int hashCode = key.hashCode();
        int index = hashCode % capacity;
        Node<K, V> node = new Node<>(key, value);
        if (table[index] == null) {
            table[index] = node;
        } else {
            Node<K, V> cur = table[index];
            while (cur.next != null) cur = cur.next;
            cur.next = node;
        }
    }

    public V get(K key) {
        int hashCode = key.hashCode();
        int index = hashCode % capacity;
        Node<K, V> cur = table[index];
        if (cur == null) return null;
        else {
            while (cur != null && !cur.key.equals(key)) cur = cur.next;
            if (cur == null) return null;
            else return cur.value;
        }
    }



    public static void main(String[] args) {
        MyHashMap<String, Integer> map = new MyHashMap<>(5);

        map.put("key1", 100);
        map.put("key2", 200);
        map.put("key3", 300);
        map.put("key4", 400);
        map.put("key5", 500);
        map.put("key6", 600);

        int res1 = map.get("key1");
        System.out.println(res1);

        int res6 = map.get("key6");
        System.out.println(res6);
    }

    static class Node <K, V> {
        K key;
        V value;
        Node<K, V> next;
        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            this.next = null;
        }
    }
}

测试结果