Java集合与数据结构-哈希表

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哈希桶解决哈希冲突：

import java.util.Arrays;
import java.util.Objects;

public class HashBucket<K,V> {
    static class Node<K,V> {
        public K key;
        public V val;
        public Node<K,V> next;

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

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        HashBucket<?, ?> that = (HashBucket<?, ?>) o;
        return usedSize == that.usedSize &&
                Arrays.equals(array, that.array);
    }

    @Override
    public int hashCode() {
        int result = Objects.hash(usedSize);
        result = 31 * result + Arrays.hashCode(array);
        return result;
    }

    public Node[] array;
    public int usedSize;

    public HashBucket() {
        this.array = new Node[8];
    }

    public void put(K key, V val) {
        Node<K,V> node = new Node<K,V>(key,val);
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null) {
            if (cur.key.equals(key)) {
                cur.val = val;
                return;
            }
            cur = cur.next;
        }
        node.next = array[index];
        array[index] = node;
        this.usedSize++;
        if (loadFactor() >= 0.75) {
            resize();
        }
    }
    //扩容
    public void resize() {
        Node[] newArray = new Node[array.length * 2];
        //遍历原来的数组，每个元素重新进行哈希
        for (int i = 0; i < array.length; i++) {
            Node<K,V> cur = array[i];
            while (cur != null) {
                int hash = cur.hashCode();
                int index = hash % newArray.length;
                Node<K,V> curNext = cur.next;
                cur.next = newArray[index];
                newArray[index] = cur;
                cur = curNext;
            }
        }
    }

    //求负载因子
    public double loadFactor() {
        return usedSize * 1.0 / array.length;
    }

    public V get(K key) {
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null) {
            if (cur.key == key) {
                return cur.val;
            }
            cur = cur.next;
        }
        return null;//没找到
    }

    public static void main(String[] args) {
        HashBucket<String,Integer> hashBucket = new HashBucket<>();
        hashBucket.put("zm",1);
        hashBucket.put("zm2",2);
        System.out.println(hashBucket.get("zm2"));
    }
}

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