Java并发编程之ReentrantLock可重入锁的实例代码

// 获取锁
reentrantLock.lock();
try {
 // 临界区
} finally {
 // 释放锁
 reentrantLock.unlock();
}

public class TestReentranLock1 {
 static ReentrantLock lock = new ReentrantLock();
 public static void main(String[] args) {
  method1();
 }
 public static void method1() {
  lock.lock();
  try {
   System.out.println("execute method1");
   method2();
  } finally {
   lock.unlock();
  }
 }
 public static void method2() {
  lock.lock();
  try {
   System.out.println("execute method2");
   method3();
  } finally {
   lock.unlock();
  }
 }
 public static void method3() {
  lock.lock();
  try {
   System.out.println("execute method3");
  } finally {
   lock.unlock();
  }
 }
}

execute method1
execute method2
execute method3

public class TestReentranLock2 {
 public static void main(String[] args) {
  ReentrantLock lock = new ReentrantLock();
  Thread t1 = new Thread(() -> {
   try {
    //如果没有竞争，此方法就会获取lock对象的锁
    //如果有竞争，就进入阻塞队列等待，可以被其它线程用interrupt打断
    System.out.println("尝试获得锁");
    lock.lockInterruptibly();
   } catch (InterruptedException e) {
    e.printStackTrace();
    System.out.println("等锁的过程中被打断");
    return;
   }
   try {
    System.out.println("t1获得了锁");
   } finally {
    lock.unlock();
   }
  }, "t1");
  lock.lock();
  System.out.println("主线程获得了锁");
  t1.start();
  try {
   try {
    sleep(1);
   } catch (InterruptedException e) {
    e.printStackTrace();
   }
   t1.interrupt();
   System.out.println("执行打断t1");
  } finally {
   lock.unlock();
  }
 }
}

主线程获得了锁
尝试获得锁
执行打断t1
等锁的过程中被打断
java.lang.InterruptedException
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:898)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1222)
	at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:335)
	at cn.yj.jvm.TestReentranLock2.lambda$main$0(TestReentranLock2.java:15)
	at java.lang.Thread.run(Thread.java:748)

ReentrantLock lock = new ReentrantLock();
Thread t1 = new Thread(() -> {
 System.out.println("启动...");
 lock.lock();
 try {
  System.out.println("获得了锁");
 } finally {
  lock.unlock();
 }
}, "t1");
lock.lock();
System.out.println("获得了锁");
t1.start();
try {
 sleep(1);
 t1.interrupt();
 System.out.println("执行打断");
 sleep(1);
} finally {
 System.out.println("释放了锁");
 lock.unlock();
}

public static void main(String[] args) {
  ReentrantLock lock = new ReentrantLock();
  Thread t1 = new Thread(() -> {
   System.out.println("启动...");
   if (!lock.tryLock()) {
    System.out.println("获取不到锁，立刻失败，返回");
    return;
   }
   try {
    System.out.println("获得了锁");
   } finally {
    lock.unlock();
   }
  }, "t1");
  lock.lock();
  System.out.println("获得了锁");
  t1.start();
  try {
   try {
    sleep(500);
   } catch (InterruptedException e) {
    e.printStackTrace();
   }
  } finally {
   lock.unlock();
  }
}

ReentrantLock lock = new ReentrantLock();
Thread t1 = new Thread(() -> {
 log.debug("启动...");
 try {
  if (!lock.tryLock(1, TimeUnit.SECONDS)) {
   log.debug("获取等待 1s 后失败，返回");
   return;
  }
 } catch (InterruptedException e) {
  e.printStackTrace();
 }
 try {
  log.debug("获得了锁");
 } finally {
  lock.unlock();
 }
}, "t1");
lock.lock();
log.debug("获得了锁");
t1.start();
try {
 sleep(2);
} finally {
 lock.unlock();
}

 public ReentrantLock(boolean fair) {
  sync = fair ? new FairSync() : new NonfairSync();
}

static ReentrantLock lock = new ReentrantLock();
static Condition waitCigaretteQueue = lock.newCondition();
static Condition waitbreakfastQueue = lock.newCondition();
static volatile boolean hasCigrette = false;
static volatile boolean hasBreakfast = false;
public static void main(String[] args) {
 new Thread(() -> {
  try {
   lock.lock();
   while (!hasCigrette) {
    try {
     waitCigaretteQueue.await();
    } catch (InterruptedException e) {
     e.printStackTrace();
    }
   }
   log.debug("等到了它的烟");
  } finally {
   lock.unlock();
  }
 }).start();
 new Thread(() -> {
  try {
   lock.lock();
   while (!hasBreakfast) {
    try {
     waitbreakfastQueue.await();
    } catch (InterruptedException e) {
     e.printStackTrace();
    }
   }
   log.debug("等到了它的早餐");
  } finally {
   lock.unlock();
  }
 }).start();
 sleep(1);
 sendBreakfast();
 sleep(1);
 sendCigarette();
}
private static void sendCigarette() {
 lock.lock();
 try {
  log.debug("送烟来了");
  hasCigrette = true;
  waitCigaretteQueue.signal();
 } finally {
  lock.unlock();
 }
}
private static void sendBreakfast() {
 lock.lock();
 try {
  log.debug("送早餐来了");
  hasBreakfast = true;
  waitbreakfastQueue.signal();
 } finally {
  lock.unlock();
 }
}