JAVA多线程同步的几种方法(以售票为例)

1.同步代码块

//多窗口卖100张电影票
public class Ticket implements Runnable{
	private int tickets=100;
	//锁对象,随意对象,只要保证唯一即可
	private Object obj=new Object();
	@Override
	public void run() {
		while(true){
			synchronized (obj){
				if (tickets>0){
					try {
						//线程休眠50ms
						Thread.sleep(50);
						System.out.println(Thread.currentThread().getName()+"...剩余票数:"+--tickets);
					}catch (Exception e){
						e.printStackTrace();
					}
				}else {
					return;
				}
			}
		}
	}
}

2.同步方法

//多窗口卖100张电影票
public class Ticket implements Runnable{
	private int tickets=100;
	@Override
	public void run() {
		while(true){
			ticket();
		}
	}


//同步方法,默认有锁对象,锁对象是它本身
private synchronized void ticket(){
	if (tickets>0){
		try {
			//线程休眠50ms
			Thread.sleep(50);
			System.out.println(Thread.currentThread().getName()+"...剩余票数:"+--tickets);
		}catch (Exception e){
			e.printStackTrace();
		}
	}else {
		return;
	}
}
}

3.同步锁

//多窗口卖100张电影票
public class Ticket implements Runnable{
	private int tickets=100;
	//创建锁对象,true表示是个公平锁,多个线程轮流执行
	Lock lock=new ReentrantLock(true);
	@Override
	public void run() {
		while(true) {
			try {
				//锁方法
				lock.lock();
				//线程休眠50ms
				Thread.sleep(50);
				if(tickets>0){
					System.out.println(Thread.currentThread().getName() + "...剩余票数:" + --tickets);
				}
			} catch (Exception e) {
				e.printStackTrace();
			}finally {
				//需解锁
				lock.unlock();
			}
		}
	}

}