Java随笔记 - Java代码实现一个死锁程序

Java随笔记 - Java代码实现一个死锁程序

死锁demo

• 线程死锁是一个经典的多线程问题，因为不同的线程都在等待根本不可能释放的资源，从而导致所有的任务都无法继续完成。这里就不再赘述理论细节，主要是要用代码简单实现一个死锁的程序，具体代码如下：

  // new两个对象用来作为锁
  // 两个方法，方法A先获得obj1的锁，睡眠一秒后，尝试去获取obj2的锁
  // 方法B先获得obj2的锁，睡眠一秒后，尝试去获取obj1的锁
  // 两个方法错开，分别拥有一个锁，再去获取对方手里的锁，就会进入死锁状态
  
  public class DeadLock {
  
      private Object obj1 = new Object();
      private Object obj2 = new Object();
  
      public void methodA() {
          synchronized (obj1) {
              System.out.println(Thread.currentThread().getName() + " - get the lock of obj1.");
              try {
                  Thread.sleep(1000);
              } catch (InterruptedException e) {
                  e.printStackTrace();
              }
              System.out.println(Thread.currentThread().getName() + " - to get the lock of obj2...");
              synchronized (obj2) {
                  System.out.println(Thread.currentThread().getName() + " - get the lock of obj2.");
              }
          }
      }
  
      public void methodB() {
          synchronized (obj2) {
              System.out.println(Thread.currentThread().getName() + " - get the lock of obj2.");
              try {
                  Thread.sleep(1000);
              } catch (InterruptedException e) {
                  e.printStackTrace();
              }
              System.out.println(Thread.currentThread().getName() + " - to get the lock of obj1...");
              synchronized (obj1) {
                  System.out.println(Thread.currentThread().getName() + " - get the lock of obj1.");
              }
          }
      }
  
  }
  

  public class ServiceA implements Runnable {
  
      private DeadLock deadLock;
  
      public ServiceA(DeadLock deadLock) {
          this.deadLock = deadLock;
      }
  
      @Override
      public void run() {
          deadLock.methodA();
      }
  }
  
  public class ServiceB implements Runnable {
  
      private DeadLock deadLock;
  
      public ServiceB(DeadLock deadLock) {
          this.deadLock = deadLock;
      }
  
      @Override
      public void run() {
          deadLock.methodB();
      }
  }
  
  public static void main(String[] args) {
          DeadLock deadLock = new DeadLock();
          Thread threadA = new Thread(new ServiceA(deadLock));
          Thread threadB = new Thread(new ServiceB(deadLock));
          threadA.start();
          threadB.start();
  }