死鎖產生的原因（必須有兩個執行緒、必須有多個鎖、鎖之間必須有引用的過程）

package com.cppdy;

class MyThread9 implements Runnable {

    private Integer ticketCount = 100;
    private Object ob = new Object();
    public boolean falg = true;

    @Override
    public void run() {
        if (falg) {
            synchronized (ob) {
                
 
while (ticketCount > 0) {
                    try {
                        Thread.sleep(50);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    synchronized (this) {
                        System.out
                                .println(Thread.currentThread().getName() 
 
+ "賣出了第：" + (100 - ticketCount + 1) + "張票。");
                        ticketCount--;
                    }
                }
            }
        } else {
            while (ticketCount > 0) {
                sale();
            }
        }
    }

    public synchronized void sale() {
        synchronized
 
 (ob) {
            if (ticketCount > 0) {
                try {
                    Thread.sleep(50);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + "賣出了第：" + (100 - ticketCount + 1) + "張票。");
                ticketCount--;
            }
        }
    }
}

public class ThreadDemo9 {

    public static void main(String[] args) throws Exception {
        MyThread9 mt = new MyThread9();
        Thread thread1 = new Thread(mt, "視窗1");
        Thread thread2 = new Thread(mt, "視窗2");
        thread1.start();
        Thread.sleep(30);
        mt.falg = false;
        thread2.start();
    }

}

T1一直等待T2釋放this鎖

T2又一直等待T1釋放ob鎖