Java ReentrantLock getQueuedThreads() Method

by Online Tutorials Library July 22, 2022

Java Reentrantlock getQueuedThreads()Method

The getQueuedThreads() returns a collection containing threads that may be waiting to acquire this lock. Because the actual threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate.

Syntax

Parameter

No parameter is passed.

Returns

the collection of threads

Throws

No Exception is thrown.

Example 1

  package com.app.Rentrant;       import java.util.concurrent.locks.ReentrantLock;        public class ReentrantLockgetQueuedThreadExample1 {        public static void main(String[] args) {                    ReentrantLock lock=new ReentrantLock();               MyRunnableClass myRnbl=new MyRunnableClass(lock);               new Thread(myRnbl,”Thread-1″).start();                                   }    }           class MyRunnableClass implements Runnable{                ReentrantLock lock;        public MyRunnableClass(ReentrantLock lock) {                this.lock=lock;        }                public void run(){                              System.out.println(Thread.currentThread().getName()                            +” is Waiting to get the lock”);                              lock.lock();                    System.out.println(Thread.currentThread().getName()                            +” has got the  lock.”);                              try {                      Thread.sleep(2000);               } catch (InterruptedException e) {                      e.printStackTrace();               }                         System.out.println(” getQueueLength = “+lock.getQueueLength()+”  “);                              System.out.println(Thread.currentThread().getName()                            +” has released the lock.”);                              lock.unlock();            }    }  

Test it Now

Output:

Thread-1 is Waiting to get the lock  Thread-1 has got the lock.   getQueueLength = 0    Thread-1 has released the lock.

Example 2

  package com.app.Rentrant;       import java.util.concurrent.locks.ReentrantLock;        public class ReentrantLockgetQueuedThreadExample2 {        public static void main(String[] args) {                    ReentrantLock lock=new ReentrantLock();               MyRunnableClass1 myRnbl=new MyRunnableClass1(lock);               new Thread(myRnbl,”Thread-1″).start();               new Thread(myRnbl,”Thread-2″).start();               new Thread(myRnbl,”Thread-3″).start();                       }    }           class MyRunnableClass1 implements Runnable{                ReentrantLock lock;        public MyRunnableClass1(ReentrantLock lock) {                this.lock=lock;        }                public void run(){                              System.out.println(Thread.currentThread().getName()                            +” is Waiting to get the lock”);                              lock.lock();                    System.out.println(Thread.currentThread().getName()                            +” has got the  lock.”);                              try {                      Thread.sleep(2000);               } catch (InterruptedException e) {                      e.printStackTrace();               }                         System.out.println(“getQueueLength = “+lock.getQueueLength());                              System.out.println(Thread.currentThread().getName()                            +” has released  the lock.”);                              lock.unlock();    //read explanation for 5sec        }    }  

Test it Now

Output:

Thread-1 is Waiting to get the lock  Thread-3 is Waiting to get the lock  Thread-1 has got the lock.  Thread-2 is Waiting to get the lock  getQueueLength = 2  Thread-1 has released the lock.  Thread-3 has got the lock.  getQueueLength = 1  Thread-3 has released the lock.  Thread-2 has got the lock.  getQueueLength = 0  Thread-2 has released the lock.

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