线程不安全
1.下面这一例子会造成线程不安全 会取出负数,会同时一起抢 要是剩最后一张票的时候 会同时取出一,这样就造成线程不安全 //不安全买票 public class UnsafeBuyTicket { public static void main(String[] args) { BuyTicket station = new BuyTicket(); new Thread(station,"苦逼的我").start(); new Thread(station,"牛逼的你").start(); new Thread(station,"可恶的黄牛党").start(); } } class BuyTicket implements Runnable{ //票 private int ticketNnums = 10; boolean flag = true;//外部停止 public void run(){ //买票 while(flag){ try { buy(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void buy() throws InterruptedException { //判断是否有票 if (ticketNnums<=0){ flag = false; return; } //模拟延时 Thread.sleep(1000); //买票 System.out.println(Thread.currentThread().getName()+"拿到"+ticketNnums--); } } ------------------------------------------------------------------------------------ 2.
在buys()方法前面加synchronized它是同步方法锁的是(this)当前这个方法
synchronized 作用是使当前的线程能有序地进出
public class UnsafeBuyTicket { public static void main(String[] args) { BuyTicket station = new BuyTicket(); new Thread(station,"苦逼的我").start(); new Thread(station,"牛逼的你").start(); new Thread(station,"可恶的黄牛党").start(); } } class BuyTicket implements Runnable{ //票 private int ticketNnums = 10; boolean flag = true;//外部停止 public void run(){ //买票 while(flag){ try { buy(); } catch (InterruptedException e) { e.printStackTrace(); } } } private synchronized void buy() throws InterruptedException { //判断是否有票 if (ticketNnums<=0){ flag = false; return; } //模拟延时 Thread.sleep(1000); //买票 System.out.println(Thread.currentThread().getName()+"拿到"+ticketNnums--); } }