Java多线程同步问题：死锁案例-蒲公英云

Java多线程同步问题：死锁案例

原创妖狐艹你老母 2024-10-08 02:03 176阅读 0赞

死锁是多线程编程中的一种严重问题。当两个或更多的线程在执行过程中，因争夺资源而造成的一种互相等待的现象称为死锁。

下面是一个简单的死锁案例：

// 定义两个共享资源
class Resource {
    private int count = 0;
    // 让一个线程增加count,另一个线程减少count
    public synchronized void increse() { count++; }
    public synchronized void decrease() { count--; if(count < 0) throw new RuntimeException("Invalid state"); }
    // 获取当前的count值，需要同步
    public synchronized int getCount() { return count; }
}
// 定义两个线程，每个线程都需要资源
class WorkerThread implements Runnable {
    private Resource resource;
    public WorkerThread(Resource resource) { this.resource = resource; }
    @Override
    public void run() {
        try {
            // 线程A:增加count
            while (true) {
                if (resource.increase()) {
                    System.out.println("Thread A increased count to " + resource.getCount());
                    break;
                } else {
                    System.out.println("Thread A couldn't increase count");
                    Thread.sleep(1000);
                }
            }
            // 线程B:减少count
            while (true) {
                if (resource.decrease()) {
                    System.out.println("Thread B decreased count to " + resource.getCount());
                    break;
                } else {
                    System.out.println("Thread B couldn't decrease count");
                    Thread.sleep(1000);
                }
            }
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
    }
}
// 主程序，启动两个线程
public class Main {
    public static void main(String[] args) {
        Resource resource = new Resource();
        Thread threadA = new Thread(new WorkerThread(resource)));
        Thread threadB = new Thread(new WorkerThread(resource)));
        // 启动线程
        threadA.start();
        threadB.start();
        // 等待所有线程完成
        try {
            threadA.join();
            threadB.join();
        } catch (InterruptedException e) {
            System.err.println(e.getMessage());
        }
    }
}