Java线程同步

/*
 * 1.同步方法
 * synchronized 方法声明
 * {
 * 		//方法体
 * }
 * 
 * 2.同步块
 * synchronized(资源对象)
 * {
 * 		//需要进行同步的方法
 * }
 * 
 */

1.代码示例:

public class ThreadClass{
	public static void main(String args[]) {
		Printer pr = new Printer();
		Teacher th1 = new Teacher(pr, "Marks", 56, 89, 78);
		Teacher th2 = new Teacher(pr, "Hello", 67, 76, 82);
		Teacher th3 = new Teacher(pr, "World", 80, 90, 70);
		th1.th.start();
		th2.th.start();
		th3.th.start();
	}
}

class Printer {
	
	//方法一.同步方法来实现线程同步
//	synchronized void  printScore(String name,int score1,int score2,int score3) {
	
	synchronized void  printScore(String name,int score1,int score2,int score3) {
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println(name+"的成绩");
		System.out.println(name+"英语:"+score1);
		System.out.println(name+"数学:"+score2);
		System.out.println(name+"语文:"+score3);
		
	}
}

class Teacher implements Runnable {
	Printer ps = null;
	String name = null;
	Thread th;
	int score1;
	int score2;
	int score3;
	
	Teacher(Printer ps,String name,int score1,int score2,int score3) {
		this.ps = ps;
		this.name =name;
		th = new Thread(this);
		this.score1 = score1;
		this.score2 = score2;
		this.score3 = score3;
	}
	
	public  void  run() {
		//方法二.使用同步代码块来实现同步;
		synchronized (ps) {
			ps.printScore(name, score1, score2, score3);
		}
	}
}	

结果:

Marks的成绩
Marks英语:56
Marks数学:89
Marks语文:78
World的成绩
World英语:80
World数学:90
World语文:70
Hello的成绩
Hello英语:67
Hello数学:76
Hello语文:82

2.Java的同步是通过锁的机制来实现

代码示例:

class Source {
	//定义同步方法 method1;
	synchronized void method1() {
		System.out.println("进入方法method1,获得锁");
		try {
			Thread.sleep(1000);		//线程休眠
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("method1方法执行完毕,释放锁");
	}
	//定义同步方法 method2;
	synchronized void method2() {
		System.out.println("进入方法method2,获得锁");
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("method2方法执行完毕,释放锁");
	}
}

class MyThread implements Runnable {
	String name;
	Source s = null;
	MyThread(Source s,String name) {
		this.s = s;
		this.name = name;
	}
	public void run() {
		if("method1" == name) {
			s.method1();			//调用同步方法1
		}
		else {
			System.out.println("Thread2启动...准备调用method2方法");
			s.method2();			//调用同步方法2
		}
	}
}

public class ThreadClass {
	public static void main(String args[]) {
		Source s = new Source();		//创建一个资源对象
		//创建两个实现Runnable接口的对象
		MyThread mt1 = new MyThread(s, "method1");
		MyThread mt2 = new MyThread(s, "method2");
		//创建两个线程
		Thread t1 = new Thread(mt1);
		Thread t2 = new Thread(mt2);
		//启动线程
		t1.start();
		t2.start();
	}
}

结果:

进入方法method1,获得锁
Thread2启动...准备调用method2方法
method1方法执行完毕,释放锁
进入方法method2,获得锁
method2方法执行完毕,释放锁