java 线程安全问题

1.同步代码块

1.1 使用 synchronized 解决 Runnable 线程安全问题

ps: 使用同一个obj 的锁

package com.cj;

class WindowsTest2 implements  Runnable{
    private int ticket = 100;
    Object obj = new Object();
    public void run() {
        while (true){
            synchronized (obj){
                if(ticket>0){
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "卖票："+"票号："+ticket);
                    ticket--;
                }else{
                    break;
                }
            }


        }

    }
}
class Test2{
    public static void main(String[] args) {
        WindowsTest2 windowsTest2 = new WindowsTest2();
        Thread w1 = new Thread(windowsTest2);
        Thread w2 = new Thread(windowsTest2);
        Thread w3 = new Thread(windowsTest2);

        w1.setName("窗口1");
        w2.setName("窗口2");
        w3.setName("窗口3");
        w1.start();
        w2.start();
        w3.start();
    }
}

1.2  解决 extends Thread 线程安全问题

package com.cj;

class WindowsTest extends Thread{
    private static int ticket = 100;
    private static Object obj = new Object();
    @Override
    public void run() {
        while (true){
            synchronized (obj){
                if(ticket>0){
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "卖票："+"票号："+ticket);
                    ticket--;
                }else{
                    break;
                }
            }
        }

    }
}
class Test{
    public static void main(String[] args) {
        WindowsTest w1 = new WindowsTest();
        WindowsTest w2 = new WindowsTest();
        WindowsTest w3 = new WindowsTest();
        w1.setName("窗口1");
        w2.setName("窗口2");
        w3.setName("窗口3");
        w1.start();
        w2.start();
        w3.start();
    }
}

2 同步方法

package com.cj;

public class WindowsTest3 implements Runnable{
    private int ticket = 100;
    public void run() {
        while (true){
            show();
        }
    }
    public synchronized void show(){
        if(ticket>0){
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "卖票："+"票号："+ticket);
            ticket--;
        }
    }

}

class Test3{
    public static void main(String[] args) {
        WindowsTest3 windowsTest3 = new WindowsTest3();
        Thread w1 = new Thread(windowsTest3);
        Thread w2 = new Thread(windowsTest3);
        Thread w3 = new Thread(windowsTest3);

        w1.setName("窗口1");
        w2.setName("窗口2");
        w3.setName("窗口3");
        w1.start();
        w2.start();
        w3.start();
    }
}