Java高并发之同步异步

package com.thread;

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

/**
 * 同步方法
 * @author Administrator
 *
 */
public class SynchronizedMethod implements Runnable{

    //静态共享变量 i
    static int i = 0;
    
    /**
     * 自增
     */
    public synchronized void increase(){
        i++;
    }
    
    @Override
    public void run() {
        for (int j = 0; j < 100; j++) {
            increase();
        }
    }
    
    public static void main(String[] args) throws InterruptedException {
        SynchronizedMethod instance = new SynchronizedMethod();
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        for (int i = 0; i < 3; i++) {
            //同一实例，线程共享静态变量i
//            executorService.execute(instance);
            //不同实例，线程单独享有变量i，达不到同步目的
            executorService.execute(new SynchronizedMethod());
            /**
             * 由于线程执行时间过短，在不同实例下，可能会得到类似于同步的结果。
             */
            Thread.sleep(100);
        }
        
        executorService.shutdown();
        
        System.out.println(i);  //300
        
    }
}

package com.thread;

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

/**
 * 同步代码块
 * @author Administrator
 *
 */
public class SynchronizedCodeBlock implements Runnable{

    //静态共享变量 i
    static int i = 0;
    
    @Override
    public void run() {
        //同步进来的对象
        synchronized(this){  //SynchronizedCodeBlock.class
            for (int j = 0; j < 100; j++) {
                i++;
            }
        }
    }
    
    public static void main(String[] args) throws InterruptedException {
        SynchronizedCodeBlock instance = new SynchronizedCodeBlock();
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        for (int i = 0; i < 3; i++) {
//            executorService.execute(instance);
            executorService.execute(new SynchronizedCodeBlock());
            Thread.sleep(10);
        }
        
        executorService.shutdown();
        
        System.out.println(i);  //300
        
    }
}