实现HashTable

完全不是当年考研中数据结构里的hash表，当时书中只说如何存放，冲突怎么处理，一直以为存的就是一个元素，后来一想get时输入什么呢，一看jdk源码才知道，原来存的是键值对，是两个元素，与HashMap相似！！看来不能读死书啊，要活学活用！

/** * Title: HashTableCuston * Description: * * @date 2017/12/24 18:51 */public class HashTableCuston<K, V> {    private Entry<?, ?>[] table;    private int capacity;    public HashTableCuston() {//默认构造函数，暂时未加入装载因子，未完待续        this(11);    }    public HashTableCuston(int capacity) {        if(capacity < 0){            throw new  IllegalArgumentException("Illegal capacity :"+capacity);        }        this.capacity = capacity;        table = new Entry<?, ?>[capacity];    }    private static class Entry<K, V> {        int hash;        K key;        V value;        Entry<K, V> next;        public Entry(int hash, K key, V value, Entry<K, V> next) {            this.hash = hash;            this.key = key;            this.value = value;            this.next = next;        }        public K getKey() {            return key;        }        public V getValue() {            return value;        }    }//Entry    /**     * 根据key获取value     * @param key     * @return     */    public synchronized V get(Object key){        Entry<?,?>[] tab = table;        int hash = key.hashCode() & 0X7FFFFFF ;        int index = hash % table.length;        for(Entry<?,?> entry = tab[index];entry != null ;entry = entry.next  ){            if( (entry.hash == hash) && (entry.key == entry.key) ){                return (V)entry.value;            }        }        return  null;    }    /**     * 放入键值对     *     * @param key     * @param value     * @return     */    public  synchronized V put(K key, V value) {        Entry<?, ?>[] tab = table;//Entry<?, ?>是Entry<String, Integer>等具体类的父类        int hash = key.hashCode();        int index = (hash & 0X7FFFFFF) % tab.length;        Entry<K, V> entry = (Entry<K, V>) tab[index];        //检查有无已存在的key        for (; entry != null; entry = entry.next) {            if ((entry.hash == hash) && entry.key == key) {                V oldValue = entry.value;                entry.value = value;                return oldValue;            }        }        addEntry(hash, key, value, index);        return null;    }    /**     * 创建新的结点     *     * @param hash     * @param key     * @param value     * @param index     */    private void addEntry(int hash, K key, V value, int index) {        Entry<?, ?>[] tab = table;        Entry<K, V> entry = (Entry<K, V>) tab[index];//之前已存在结点        tab[index] = new Entry<>(hash, key, value, entry);//之前已存在的结点作为后继结点    }}

    public static void main(String[] args) {        HashTableCuston<String, Integer> hashtable = new HashTableCuston<String, Integer>(5);        hashtable.put("one", 1);        hashtable.put("two", 2);        hashtable.put("three", 3);        hashtable.put("four", 4);        hashtable.put("five", 5);        hashtable.put("six", 6);        hashtable.put("seven", 7);        Integer v = hashtable.get("six");//输出6        System.out.println(v);    }