java ReentrantLock Explanation
- 2021-07-13 05:29:05
- OfStack
Introduction
The ReentrantLock is called a reentry lock and has more powerful functions than the internal lock synchonized. It can interrupt, time, and set a fair lock
[Note] When using ReentrantLock, 1 must release the lock, and 1 release it in finnal.
Provide the following important methods
lock (): Acquire the lock and wait if the lock is already occupied lockInterruptibly (): Lock acquired but limited response interrupt unlock (): Release lock tryLock (): Attempt to acquire a lock. If yes, return true; Otherwise false is returned tryLock (long time, TimeUnit unit): The lock is acquired within a given time. If true is returned; Otherwise false is returnedExample
Example 1
import java.util.concurrent.locks.ReentrantLock;
public class ReentrantLockTest {
ReentrantLock lock;
ReentrantLockTest(ReentrantLock lock) {
this.lock = lock;
}
private Runnable getRunnable() {
return new Runnable() {
@Override
public void run() {
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("break before");
break;
} else {
//System.out.println("Unable to lock " + Thread.currentThread().getName());
}
} catch (InterruptedException e){
System.out.println(Thread.currentThread() + " is Interupted");
e.printStackTrace();
}
}
}
};
}
public static void main(String[] args) {
ReentrantLock lock = new ReentrantLock();
ReentrantLockTest test = new ReentrantLockTest(lock);
ReentrantLockTest test2 = new ReentrantLockTest(lock);
Thread thread1 = new Thread(test.getRunnable(), "firstThread");
Thread thread2 = new Thread(test2.getRunnable(), "secondThread");
thread1.start();
thread2.start();
try {
Thread.sleep(300);
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("interupt begin");
thread2.interrupt();
System.out.println("interupt end");
}
}
1 execution result:
Locked:firstThread
interupt begin
interupt end
UnLocked:firstThread
break before
Locked:secondThread
UnLocked:secondThread
Thread[secondThread,5,main] is Interupted
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.jihite.templet.JavaBase.ReentrantLockTest$1.run(ReentrantLockTest.java:23)
at java.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:secondThread
break before
Analysis: When firstThread executes, secondThread constantly judges whether the lock can be obtained, and when firstThread executes, secondThread is interrupted after execution
Example 2
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
public class ReentrantLockTest {
ReentrantLock lock;
ReentrantLockTest(ReentrantLock lock) {
this.lock = lock;
}
private Runnable getRunnable() {
return new Runnable() {
@Override
public void run() {
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("break before");
break;
} else {
//System.out.println("Unable to lock " + Thread.currentThread().getName());
}
} catch (InterruptedException e){
System.out.println(Thread.currentThread() + " is Interupted");
e.printStackTrace();
}
}
}
};
}
public static void main(String[] args) {
ReentrantLock lock = new ReentrantLock();
ReentrantLockTest test = new ReentrantLockTest(lock);
ReentrantLockTest test2 = new ReentrantLockTest(lock);
Thread thread1 = new Thread(test.getRunnable(), "firstThread");
Thread thread2 = new Thread(test2.getRunnable(), "secondThread");
thread1.start();
thread2.start();
try {
Thread.sleep(300);
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("interupt begin");
thread2.interrupt();
System.out.println("interupt end");
}
}
1 execution result
Locked:firstThread
interupt begin
interupt end
Thread[secondThread,5,main] is Interupted
java.lang.InterruptedException
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireNanos(AbstractQueuedSynchronizer.java:936)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireNanos(AbstractQueuedSynchronizer.java:1247)
at java.util.concurrent.locks.ReentrantLock.tryLock(ReentrantLock.java:442)
at com.jihite.templet.JavaBase.ReentrantLockTest$1.run(ReentrantLockTest.java:19)
at java.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:firstThread
break before
UnLocked:secondThread
break before
Analysis: firstThread executes, secondThread waits, and the waiting process is interrupted. After interrupting, firstThread execution ends, secondThread gets the lock and continues execution
Example 3
import java.util.concurrent.locks.ReentrantLock;
public class ReentrantLockTest2 {
ReentrantLock lock;
ReentrantLockTest2(ReentrantLock lock) {
this.lock = lock;
}
private Runnable getRunnable() {
return new Runnable() {
@Override
public void run() {
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 (InterruptedException e) {
e.printStackTrace();
}
}
}
};
}
public static void main(String[] args) {
ReentrantLock lock = new ReentrantLock();
ReentrantLockTest2 test = new ReentrantLockTest2(lock);
ReentrantLockTest2 test2 = new ReentrantLockTest2(lock);
Thread thread1 = new Thread(test.getRunnable(), "firstThread");
Thread thread2 = new Thread(test2.getRunnable(), "secondThread");
thread1.start();
thread2.start();
try {
Thread.sleep(600);
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("interupt begin");
thread2.interrupt();
System.out.println("interupt end");
}
}
1 execution result
Locked:firstThread
interupt begin
interupt end
UnLocked:firstThread
Locked:secondThread
UnLocked:secondThread
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.jihite.templet.JavaBase.ReentrantLockTest2$1.run(ReentrantLockTest2.java:22)
at java.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:secondThread
Analysis: firstThread gets the lock execution first, secondThread is waiting, and the interrupt does not interrupt the wait. firstThread is finished, and secondThread is interrupted after being acquired
Example 4
public class ReentrantLockTest2 {
ReentrantLock lock;
ReentrantLockTest2(ReentrantLock lock) {
this.lock = lock;
}
private Runnable getRunnable() {
return new Runnable() {
@Override
public void run() {
while (true) {
try {
try {
// lock.lock();
lock.lockInterruptibly();
System.out.println("Locked:" + Thread.currentThread().getName());
Thread.sleep(800);
break;
} finally {
lock.unlock();
System.out.println("UnLocked:" + Thread.currentThread().getName());
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
}
public static void main(String[] args) {
ReentrantLock lock = new ReentrantLock();
ReentrantLockTest2 test = new ReentrantLockTest2(lock);
ReentrantLockTest2 test2 = new ReentrantLockTest2(lock);
Thread thread1 = new Thread(test.getRunnable(), "firstThread");
Thread thread2 = new Thread(test2.getRunnable(), "secondThread");
thread1.start();
thread2.start();
try {
Thread.sleep(600);
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("interupt begin");
thread2.interrupt();
System.out.println("interupt end");
}
}
1 execution result
Locked:firstThread
interupt begin
interupt end
Exception in thread "secondThread" java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:151)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1261)
at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:457)
at com.jihite.templet.JavaBase.ReentrantLockTest2$1.run(ReentrantLockTest2.java:25)
at java.lang.Thread.run(Thread.java:748)
Analysis: lock. lockInterruptibly (); Can respond to interrupt time during execution