synchronized

package com.cn;

class Test{
    public static void main(String [] args){
        TestThread t = new TestThread();
        new Thread(t).start();
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        t.str="method";
        new Thread(t).start();
    }
}

class TestThread implements Runnable {
    int tickets = 100;
    String str = new String("");
    public void run() {
        if(str.equals("method")){
            while(true){
                synchronized (this) {
                    if(tickets>0){
                        try {
                            Thread.sleep(10);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName()+" is salling ticket "+tickets--);
                    }
                }
            }
        }else{
            while(true){
                sale();
            }
        }
    }
    public synchronized void sale(){
        if(tickets>0){
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+" is salling ticket "+tickets--);
        }
    }
}

sale()方法使用的监视器对象是this，所以要实现同步代码块和sale()方法之间的同步，同步代码块检查的同步对象也应该为this