通过CountDownLatch模拟高并发下测试各种单例模式的执行结果

      单例模式一般写法有多种，那么哪种相对来说效果比较好。下面一起看看我的测试结果吧。

      我是通过CountDownLatch来模拟刚并发下，各种单例模式的执行结果。自己做加深影响所写，所以写的比较粗糙，希望大家不要介意。

先上代码吧，后面做结果说明

1、最基础的单例

package singleton;

/**
 * 最简单的单例
 */
public class MySingleton {

    private static   MySingleton mySingleton = null;

    public static MySingleton getInstance(){
        if(mySingleton == null){
            System.out.println(System.currentTimeMillis());
             mySingleton = new MySingleton();
        }
        return mySingleton;
    }
}

2、带锁的单例

package singleton;

/**
 * 最简单的单例
 */
public class MySingleton2 {

    private static MySingleton2 mySingleton = null;

    private static Object obj = new Object();

    public static MySingleton2 getInstance(){
        if(mySingleton == null){
            System.out.println(System.currentTimeMillis());
            synchronized (obj){
                if(mySingleton == null){
                    mySingleton = new MySingleton2();
                }
            }

        }
        return mySingleton;
    }
}

3、测试最简单的单例类

  

package singleton;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 测试类
 */
public class Test {
    /**
     * 模拟client_num个客户端同时访问
     */
    private static int clientNum = 1000;
    private static int threadsNum = 10;
    /**
     * 计数器
     */
    final static CountDownLatch doneSignal = new CountDownLatch(clientNum);
    public static void main(String[] args) {
        /**
         * 建立线程池
         */
        ExecutorService exec = Executors.newFixedThreadPool(threadsNum);
        for(int i=0 ; i< clientNum; i++){
             MyRunnable myRunnable = new MyRunnable();
             exec.execute(myRunnable);
             doneSignal.countDown();
         }
    }

     static class  MyRunnable implements  Runnable{
        @Override
        public void run() {
            try{
                doneSignal.await();
            }catch (Exception e){
                e.printStackTrace();
            }
            System.out.println(MySingleton.getInstance()+"=");
        }
    }

}

测试结果：

4、上锁的单例测试类

package singleton;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 测试类
 */
public class Test {
    /**
     * 模拟client_num个客户端同时访问
     */
    private static int clientNum = 100;
    private static int threadsNum = 5;
    /**
     * 计数器
     */
    final static CountDownLatch doneSignal = new CountDownLatch(clientNum);
    public static void main(String[] args) {
        /**
         * 建立线程池
         */
        ExecutorService exec = Executors.newFixedThreadPool(threadsNum);
        for(int i=0 ; i< clientNum; i++){
             MyRunnable myRunnable = new MyRunnable();
             exec.execute(myRunnable);
             doneSignal.countDown();
         }
    }

     static class  MyRunnable implements  Runnable{
        @Override
        public void run() {
            try{
                doneSignal.await();
            }catch (Exception e){
                e.printStackTrace();
            }
            System.out.println(MySingleton2.getInstance()+"=");
        }
    }

}

测试结果：