java ReentrantLock详解
介绍
ReentrantLock称为重入锁，比内部锁synchonized拥有更强大的功能，它可中断、可定时、设置公平锁
【注】使用ReentrantLock时，一定要释放锁，一般释放放到finnal里写。
提供以下重要的方法
- lock():获得锁，如果锁已被占用，则等待
- lockInterruptibly():获得锁，但有限响应中断
- unlock():释放锁
- tryLock():尝试获取锁。如果获得，返回true；否则返回false
- tryLock(longtime,TimeUnitunit):在给定时间内获得锁。如果获得返回true；否则返回false
示例
例子1
importjava.util.concurrent.locks.ReentrantLock;
publicclassReentrantLockTest{
ReentrantLocklock;
ReentrantLockTest(ReentrantLocklock){
this.lock=lock;
}
privateRunnablegetRunnable(){
returnnewRunnable(){
@Override
publicvoidrun(){
while(true){
try{
if(lock.tryLock()){
try{
System.out.println("Locked:"+Thread.currentThread().getName());
Thread.sleep(800);
}finally{
lock.unlock();
System.out.println("UnLocked:"+Thread.currentThread().getName());
}
System.out.println("breakbefore");
break;
}else{
//System.out.println("Unabletolock"+Thread.currentThread().getName());
}
}catch(InterruptedExceptione){
System.out.println(Thread.currentThread()+"isInterupted");
e.printStackTrace();
}
}
}
};
}
publicstaticvoidmain(String[]args){
ReentrantLocklock=newReentrantLock();
ReentrantLockTesttest=newReentrantLockTest(lock);
ReentrantLockTesttest2=newReentrantLockTest(lock);
Threadthread1=newThread(test.getRunnable(),"firstThread");
Threadthread2=newThread(test2.getRunnable(),"secondThread");
thread1.start();
thread2.start();
try{
Thread.sleep(300);
}catch(InterruptedExceptione){
e.printStackTrace();
}
System.out.println("interuptbegin");
thread2.interrupt();
System.out.println("interuptend");
}
}
一次执行结果：
Locked:firstThread
interuptbegin
interuptend
UnLocked:firstThread
breakbefore
Locked:secondThread
UnLocked:secondThread
Thread[secondThread,5,main]isInterupted
java.lang.InterruptedException:sleepinterrupted
atjava.lang.Thread.sleep(NativeMethod)
atcom.jihite.templet.JavaBase.ReentrantLockTest$1.run(ReentrantLockTest.java:23)
atjava.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:secondThread
breakbefore
分析：firstThread执行，secondThread不停的判断是否可以获得锁，当firstThread执行完，secondThread执行后被打断
例子2
importjava.util.concurrent.TimeUnit;
importjava.util.concurrent.locks.ReentrantLock;
publicclassReentrantLockTest{
ReentrantLocklock;
ReentrantLockTest(ReentrantLocklock){
this.lock=lock;
}
privateRunnablegetRunnable(){
returnnewRunnable(){
@Override
publicvoidrun(){
while(true){
try{
if(lock.tryLock(700,TimeUnit.MILLISECONDS)){
try{
System.out.println("Locked:"+Thread.currentThread().getName());
Thread.sleep(800);
}finally{
lock.unlock();
System.out.println("UnLocked:"+Thread.currentThread().getName());
}
System.out.println("breakbefore");
break;
}else{
//System.out.println("Unabletolock"+Thread.currentThread().getName());
}
}catch(InterruptedExceptione){
System.out.println(Thread.currentThread()+"isInterupted");
e.printStackTrace();
}
}
}
};
}
publicstaticvoidmain(String[]args){
ReentrantLocklock=newReentrantLock();
ReentrantLockTesttest=newReentrantLockTest(lock);
ReentrantLockTesttest2=newReentrantLockTest(lock);
Threadthread1=newThread(test.getRunnable(),"firstThread");
Threadthread2=newThread(test2.getRunnable(),"secondThread");
thread1.start();
thread2.start();
try{
Thread.sleep(300);
}catch(InterruptedExceptione){
e.printStackTrace();
}
System.out.println("interuptbegin");
thread2.interrupt();
System.out.println("interuptend");
}
}
一次执行结果
Locked:firstThread
interuptbegin
interuptend
Thread[secondThread,5,main]isInterupted
java.lang.InterruptedException
atjava.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireNanos(AbstractQueuedSynchronizer.java:936)
atjava.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireNanos(AbstractQueuedSynchronizer.java:1247)
atjava.util.concurrent.locks.ReentrantLock.tryLock(ReentrantLock.java:442)
atcom.jihite.templet.JavaBase.ReentrantLockTest$1.run(ReentrantLockTest.java:19)
atjava.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:firstThread
breakbefore
UnLocked:secondThread
breakbefore
分析：firstThread执行，secondThread等待，等待过程被打断。打断后firstThread执行结束了，secondThread得到锁，继续执行
例子3
importjava.util.concurrent.locks.ReentrantLock;
publicclassReentrantLockTest2{
ReentrantLocklock;
ReentrantLockTest2(ReentrantLocklock){
this.lock=lock;
}
privateRunnablegetRunnable(){
returnnewRunnable(){
@Override
publicvoidrun(){
while(true){
try{
try{
lock.lock();
//lock.lockInterruptibly();
System.out.println("Locked:"+Thread.currentThread().getName());
Thread.sleep(800);
break;
}finally{
lock.unlock();
System.out.println("UnLocked:"+Thread.currentThread().getName());
}
}catch(InterruptedExceptione){
e.printStackTrace();
}
}
}
};
}
publicstaticvoidmain(String[]args){
ReentrantLocklock=newReentrantLock();
ReentrantLockTest2test=newReentrantLockTest2(lock);
ReentrantLockTest2test2=newReentrantLockTest2(lock);
Threadthread1=newThread(test.getRunnable(),"firstThread");
Threadthread2=newThread(test2.getRunnable(),"secondThread");
thread1.start();
thread2.start();
try{
Thread.sleep(600);
}catch(InterruptedExceptione){
e.printStackTrace();
}
System.out.println("interuptbegin");
thread2.interrupt();
System.out.println("interuptend");
}
}
一次执行结果
Locked:firstThread
interuptbegin
interuptend
UnLocked:firstThread
Locked:secondThread
UnLocked:secondThread
java.lang.InterruptedException:sleepinterrupted
atjava.lang.Thread.sleep(NativeMethod)
atcom.jihite.templet.JavaBase.ReentrantLockTest2$1.run(ReentrantLockTest2.java:22)
atjava.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:secondThread
分析：firstThread先获得锁执行，secondThread在等待，此时中断并未打断等待。firstThread执行完，secondThread获取后被打断
例子4
publicclassReentrantLockTest2{
ReentrantLocklock;
ReentrantLockTest2(ReentrantLocklock){
this.lock=lock;
}
privateRunnablegetRunnable(){
returnnewRunnable(){
@Override
publicvoidrun(){
while(true){
try{
try{
//lock.lock();
lock.lockInterruptibly();
System.out.println("Locked:"+Thread.currentThread().getName());
Thread.sleep(800);
break;
}finally{
lock.unlock();
System.out.println("UnLocked:"+Thread.currentThread().getName());
}
}catch(InterruptedExceptione){
e.printStackTrace();
}
}
}
};
}
publicstaticvoidmain(String[]args){
ReentrantLocklock=newReentrantLock();
ReentrantLockTest2test=newReentrantLockTest2(lock);
ReentrantLockTest2test2=newReentrantLockTest2(lock);
Threadthread1=newThread(test.getRunnable(),"firstThread");
Threadthread2=newThread(test2.getRunnable(),"secondThread");
thread1.start();
thread2.start();
try{
Thread.sleep(600);
}catch(InterruptedExceptione){
e.printStackTrace();
}
System.out.println("interuptbegin");
thread2.interrupt();
System.out.println("interuptend");
}
}
一次执行结果
Locked:firstThread
interuptbegin
interuptend
Exceptioninthread"secondThread"java.lang.IllegalMonitorStateException
atjava.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:151)
atjava.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1261)
atjava.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:457)
atcom.jihite.templet.JavaBase.ReentrantLockTest2$1.run(ReentrantLockTest2.java:25)
atjava.lang.Thread.run(Thread.java:748)
分析：lock.lockInterruptibly();在执行过程中可以响应中断时间
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