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ReentrantLock的阻塞性、可中断性

news 来源：原创 2024/9/20 8:32:03

结论：

lock() 如果没有获取到锁，会一直阻塞并尝试获取锁，直到获取到锁。
lock() 获取到锁之前，其他线程不可以中断该线程。因为线程Thread如线程t2的interrupt方法，想要中断线程，但不会真的中断，只会把t2的中断标志改变，所以线程t2还会继续运行。
lockInterruptibly() 获取到锁之前，其他线程可以中断该线程。因为对interrupt标志进行了处理

lock()阻塞获取锁。如果获取不到锁，会一直阻塞，直到获取到锁

代码：

    static void main(String[] args) {ReentrantLock reentrantLock = new ReentrantLock();// t1先获取锁Thread t1 = new Thread(()->{try {reentrantLock.lock();System.out.println("t1获取到锁");try {Thread.sleep(3000);} catch (InterruptedException e) {System.out.println("t1报错");throw new RuntimeException(e);}} finally {reentrantLock.unlock();}System.out.println("11释放锁");});System.out.println("t1 name :"+t1.getName());t1.start();// 测试重点。t2后获取锁。测试lock、lockInterruptibly方法Thread t2 = new Thread(()->{try {// 确保t先执行性Thread.sleep(1000);} catch (InterruptedException e) {System.out.println("t2报错");throw new RuntimeException(e);}try {long l = System.currentTimeMillis();reentrantLock.lock();long l1 = System.currentTimeMillis();System.out.println("t2等待获取锁的时间"+(l1-l));} finally {reentrantLock.unlock();}});System.out.println("t2 name :"+t2.getName());t2.start();
}

结果：

lockInterruptibly()。获取锁前该线程可以被中断。

代码：在上面代码的基础上，lock换成lockInterruptibly，加了个t3线程（对t2进行中断操作）

    static void main(String[] args) {ReentrantLock reentrantLock = new ReentrantLock();// t1先获取锁Thread t1 = new Thread(()->{try {reentrantLock.lock();System.out.println("t1获取到锁");try {Thread.sleep(3000);} catch (InterruptedException e) {System.out.println("t1报错");throw new RuntimeException(e);}} finally {reentrantLock.unlock();}System.out.println("11释放锁");});System.out.println("t1 name :"+t1.getName());t1.start();// 测试重点。t2后获取锁。测试lock、lockInterruptibly方法Thread t2 = new Thread(()->{try {// 确保t先执行性Thread.sleep(1000);} catch (InterruptedException e) {System.out.println("t2报错");throw new RuntimeException(e);}try {long l = System.currentTimeMillis();// reentrantLock.lock();reentrantLock.lockInterruptibly();long l1 = System.currentTimeMillis();System.out.println("t2等待获取锁的时间"+(l1-l));} catch (InterruptedException e) {System.out.println("t2获取锁失败，t2需要中断，t2要退出啦");throw new RuntimeException(e);} finally {reentrantLock.unlock();}});System.out.println("t2 name :"+t2.getName());t2.start();// 用来中断t2的Thread t3 = new Thread(()->{try {Thread.sleep(2000);} catch (Exception e) {System.out.println("t3报错");throw new RuntimeException(e);}t2.interrupt();System.out.println("t3中断t2了");});System.out.println("t3 name :"+t3.getName());t3.start();}

结果：