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java如何造成死锁

2026-03-24 02:46:42Java

死锁的基本概念

死锁是指两个或多个线程在执行过程中，因争夺资源而造成的一种互相等待的现象，导致这些线程都无法继续执行下去。死锁产生的四个必要条件包括：互斥条件、占有并等待、非抢占条件和循环等待条件。

创建死锁的代码示例

以下是一个简单的Java代码示例，展示如何通过两个线程互相持有对方需要的锁来造成死锁：

public class DeadlockExample {
    private static final Object lock1 = new Object();
    private static final Object lock2 = new Object();

    public static void main(String[] args) {
        Thread thread1 = new Thread(() -> {
            synchronized (lock1) {
                System.out.println("Thread 1: Holding lock 1...");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 1: Waiting for lock 2...");
                synchronized (lock2) {
                    System.out.println("Thread 1: Acquired lock 2!");
                }
            }
        });

        Thread thread2 = new Thread(() -> {
            synchronized (lock2) {
                System.out.println("Thread 2: Holding lock 2...");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 2: Waiting for lock 1...");
                synchronized (lock1) {
                    System.out.println("Thread 2: Acquired lock 1!");
                }
            }
        });

        thread1.start();
        thread2.start();
    }
}

死锁的产生过程

线程1首先获取lock1，然后尝试获取lock2；与此同时，线程2获取lock2并尝试获取lock1。由于两个线程互相持有对方需要的锁，且都不释放已持有的锁，导致双方都无法继续执行，形成死锁。

如何检测死锁

使用工具如jstack或VisualVM可以检测死锁。运行上述代码后，通过jstack查看线程转储，会发现类似以下输出：

java如何造成死锁

Found one Java-level deadlock:
=============================
Thread 1:
  waiting to lock monitor 0x00007f88e0003e18 (object 0x000000076ab9c1a0, a java.lang.Object),
  which is held by Thread 2
Thread 2:
  waiting to lock monitor 0x00007f88e0003d18 (object 0x000000076ab9c190, a java.lang.Object),
  which is held by Thread 1