Java HashMap实现

import java.util.ArrayList;
import java.util.List;

class Entry<K, V> {
    K key;
    V value;

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

public class Myhashmap<K, V> {
    private static final int DEFAULT_SIZE = 20;
    private int size = 0;
    public List<Entry<K, V>>[] array;

    public Myhashmap() {
        this.array = new List[DEFAULT_SIZE];
    }

    private int hash(K key) {
        int temp = key.hashCode();
        return (temp & 0x7FFFFFFF) % array.length;
    }

    public void put(K key, V value) {
        int indice = hash(key);
        if (array[indice] == null) {
            array[indice] = new ArrayList<Entry<K, V>>();
            array[indice].add(new Entry<K, V>(key, value));
            size++;
        } else {
            boolean find = false;
            for (Entry<K, V> e : array[indice]) {
                if (e.key == key) {
                    e.value = value;
                    find = true;
                }
            }
            if (!find) {
                array[indice].add(new Entry<K, V>(key, value));
                size++;
            }
        }
        if (size >= array.length / 2) {
            rehash();
        }
    }

    public V get(K key) {
        int indice = hash(key);
        if (array[indice] == null) {
            return null;
        }
        for (Entry<K, V> e : array[indice]) {
            if (e.key == key) {
                return (V) e.value;
            }
        }
        return null;
    }

    public boolean containsKey(K key) {
        int indice = hash(key);
        if (array[indice] == null) {
            return false;
        }
        for (Entry<K, V> e : array[indice]) {
            if (e.key == key) {
                return true;
            }
        }
        return false;
    }

    public int size() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    private void rehash() {
        List<Entry<K, V>>[] cur = new List[2 * array.length];
        for (int i = 0; i < array.length; i++) {
            cur[i] = array[i];
        }
        array = cur;
    }
}