ConcurrentHashMap 测试

最新推荐文章于 2025-05-31 18:50:39 发布

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本文通过使用ConcurrentHashMap进行多线程并发测试，展示了ConcurrentHashMap在高并发场景下的线程安全性。测试中创建了100个线程同时向ConcurrentHashMap中添加元素，并使用ExecutorService来管理和执行这些线程任务。

package com.huang.test.concurrent;

import java.util.*;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * ConcurrentHashMap"添加移除线程安全
 * 1.获取size用mappingCount方法（返回long，不是准确的）。
 * 2.遍历时可同时修改。
 */
public class ConcurrentHashMapTest
{
    int len = 100;
    private ConcurrentHashMap<Integer, String> map = new ConcurrentHashMap<>();
    public static void main(String[] args) {
        ConcurrentHashMapTest cht = new ConcurrentHashMapTest();
        cht.test();
    }

    private void test() {
        ExecutorService exec = Executors.newFixedThreadPool(len);
        ArrayList<Callable<Void>> tasks = new ArrayList<>();
        for(int i = 0;i < len;i++)
        {
            tasks.add(new MyCallable(map, i));
        }
        try {
            exec.invokeAll(tasks);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        printMap(map);
        exec.shutdown();
    }

    private void printMap(ConcurrentHashMap<Integer, String> map)
    {
        Set<Map.Entry<Integer, String>> ks = map.entrySet();
        TreeMap<Integer, String> treeMap = new TreeMap<>();
        for(Map.Entry<Integer, String> item:ks)
        {
            int key = item.getKey();
            String value = item.getValue();
            treeMap.put(key, value);
        }

        Set<Map.Entry<Integer, String>> es = treeMap.entrySet();
        System.out.println("size:" + map.mappingCount());
        for(Map.Entry<Integer, String> item:es)
        {
            System.out.println(item.getKey() + " " + item.getValue());
        }
    }

    class MyCallable implements Callable<Void>{
        private int sec;
        private ConcurrentHashMap<Integer, String> map;

        public MyCallable(ConcurrentHashMap<Integer, String> map, int sec)
        {
            this.map = map;
            this.sec = sec;
        }

        @Override
        public Void call() {
            map.put(sec, "value" + sec);
            return null;
        }
    }
}