ConcurrentHashMap源码解读[面试专题]（集合相关）

package com.gtf.xc;

import java.util.HashMap;

public class MyConcurrentHashMap
        <K, V> {
    /**
     * segments
     */
    private HashMap<K,V>[] segments;
    public MyConcurrentHashMap() {
        segments=new HashMap[16];
        //注意是懒加载
    }
    public void put(K key, V value) {
        //第一次计算key,计算key存放在哪一个hashtable
        int segmentsIndex =key.hashCode()& (segments.length  - 1);
        HashMap<K, V> segment = segments[segmentsIndex];
        //segment == null
        if (segment == null) {
            segment=new HashMap<>();
        }
        segment.put(key,value);
        segments[segmentsIndex]=segment;
    }
    public V get(K key) {
        int segmentsIndex =key.hashCode()& (segments.length  - 1);
        HashMap<K, V> segment = segments[segmentsIndex];
        if (segment != null) {
          return  segment.get(key);
        }
        return null;
    }

    public static void main(String[] args) {
        MyConcurrentHashMap<Object, Object> objectObjectMyConcurrentHashMap = new MyConcurrentHashMap<>();
        for (int i = 0; i < 10; i++){
            objectObjectMyConcurrentHashMap.put(i,i);
        }
       for (int i = 0; i < 10; i++) {
           objectObjectMyConcurrentHashMap.get(i);
           System.out.println( objectObjectMyConcurrentHashMap.get(i));
       }

    }
}