java自实现hashmap数据结构

java自实现hashmap数据结构

Design a HashMap without using any built-in hash table libraries.

Implement the MyHashMap class:

MyHashMap() initializes the object with an empty map. void put(int
key, int value) inserts a (key, value) pair into the HashMap. If the
key already exists in the map, update the corresponding value. int
get(int key) returns the value to which the specified key is mapped,
or -1 if this map contains no mapping for the key. void remove(key)
removes the key and its corresponding value if the map contains the
mapping for the key.

class MyHashMap {
	//双值存储节点
    private class Pair{
        private int key;
        private int value;

        public Pair() {}

        public Pair(int key, int value) {
            this.key = key;
            this.value = value;
        }

        public int getKey() {
            return key;
        }

        public void setKey(int key) {
            this.key = key;
        }

        public int getValue() {
            return value;
        }

        public void setValue(int value) {
            this.value = value;
        }
    }

	//设置哈希算法
    private static final int base = 888;
    //设链表数组
    private linkedList[] data;

	//初始化
    public MyHashMap() {
        data = new linkedList[base];
        for (int i = 0; i < base; i++) {
            data[i] = new linkedList();
        }
    }

	//哈希函数
    public int hash(int key){return key%base;}
    
    //存值
    public void put(int key, int value) {
        int h = hash(key);
        Iterator iterator =  data[h].iterator();
        //顺着链表查找，找到就覆盖
        while (iterator.hasNext()){
            Pair pair = iterator.next();
            if (pair.getKey() == key) {
                pair.setValue(value);
                return;
            }
        }
        //找不到，尾部新增
        data[h].offerLast(new Pair(key,value));
    }
    
    //取值
    public int get(int key) {
        int h = hash(key);
        Iterator iterator = data[h].iterator();
        while (iterator.hasNext()){
            Pair pair = iterator.next();
            //找到了，就返回
            if (pair.getKey() == key) {
                return pair.getValue();
            }
        }
        //找不到-1
        return -1;
    }
    
    //移除
    public void remove(int key) {
        int h = hash(key);
        Iterator iterator = data[h].iterator();
        while (iterator.hasNext()){
            Pair pair = iterator.next();
            //找到了，移除
            if (pair.getKey() == key) {
                data[h].remove(pair);
                return;
            }
        }
    }
}