Java ReentrantLock isLocked() Method

The isLocked() method of ReentrantLock class checks if any thread occupies this lock. This method is created for use in monitoring of the system state, not for synchronization control.

Syntax

Parameter

No parameter is passed.

Returns

true if any thread holds this lock and false otherwise

Throws

No exception is thrown

Example 1

//import statement

import java.text.SimpleDateFormat; 
import java.util.Date; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
import java.util.concurrent.locks.ReentrantLock; 
  
class WorkerClass23 implements Runnable 
{ 
  String nm; 
  ReentrantLock relc; 
  public WorkerClass23(ReentrantLock rl, String n) 
  { 
    relc = rl; 
    nm = n; 
  } 
  public void run() 
  { 
    boolean dn = false; 
    while (!dn) 
    { 
      //Outer Lock 
      boolean ans = relc.tryLock(); 
  
      //  True if lock is free 
      if(ans) 
      { 
        try
        { 
          int i=0;
          for(i=0;i<=6;i++) {
        	  
        	  if(i>=2)
        	  {
        		  Thread t = new Thread();
        		  System.out.println("Thread Created.....");
        		  if(i==3) {
        			  t.setName("Maint Thread2");
        			  System.out.println("Thread Created.....");
        		  }
        		
        		  
        	  }
        	  if(i==4)
        		  break;
        	  
          }
          
          System.out.println(" after sleep(1500) Is locked - " + relc.isLocked()); 
          System.out.println("task name - " + nm + " work done"); 
  
          dn = true; 
        } 
        catch(Exception e) 
        { 
          e.printStackTrace(); 
        } 
        
      } 
      } 
    } 
  } 
 
  
public class ReentrantLockisLockedExample1 
{ 
  static final int MAX_Time = 2; 
  public static void main(String[] args) 
  { 
    ReentrantLock rel = new ReentrantLock(); 
    ExecutorService pool = Executors.newFixedThreadPool(MAX_Time); 
    Runnable wrk1 = new WorkerClass23(rel, "Job1"); 
    pool.execute(wrk1); 
    pool.shutdown(); 
  } 
}

Test it Now

Output:

Thread Created.....
Thread Created.....
Thread Created.....
Thread Created.....
 after sleep(1500) Is locked - true
task name - Job1 work done

Example 2

//import statements

import java.text.SimpleDateFormat; 
import java.util.Date; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
import java.util.concurrent.locks.ReentrantLock; 
  
class WorkerClass24 implements Runnable 
{ 
  String nm; 
  ReentrantLock relc; 
  public WorkerClass24(ReentrantLock rl, String n) 
  { 
    relc = rl; 
    nm = n; 
  } 
  public void run() 
  { 
    boolean dn = false; 
    while (!dn) 
    { 
      //Outer Lock 
      boolean ans = relc.tryLock(); 
  
      //  True if lock is free 
      if(ans) 
      { 
        try
        { 
        	int i=1;
        	Thread t=new Thread();
          while(i<5) {
        	  
        	  System.out.println("     "+t.getThreadGroup());
        	  if(i==2)
            System.out.println("     "+t.getThreadGroup());
        	  if(i==3)
            System.out.println("     "+t.isInterrupted());
        	  if(i==4)
            System.out.println("     "+t.getStackTrace());
        	  
        	  i=i+1;
          }
        	  
         if(relc.isLocked())
         {
        	 
         }
         else {
        	 assert !relc.isHeldByCurrentThread();
             relc.lock();
         }
  
                    
          System.out.println(" after sleep(1500) Is held by Current Thread - " + relc.isHeldByCurrentThread()); 
          System.out.println("task name - " + nm + " work done"); 
  
          dn = true; 
        } 
         
        finally {
        	relc.unlock();
        }     
      }     
      } 
    } 
  
  
  } 
 
  
public class ReentrantLockisLockedExample2 
{ 
  static final int MAX_Time = 2; 
  public static void main(String[] args) 
  { 
    ReentrantLock rel = new ReentrantLock(); 
    ExecutorService pool = Executors.newFixedThreadPool(MAX_Time); 
    Runnable wrk1 = new WorkerClass24(rel, "Job1"); 
    pool.execute(wrk1); 
    pool.shutdown(); 
  } 
}

Test it Now

Output:

  java.lang.ThreadGroup[name=main,maxpri=10]
     java.lang.ThreadGroup[name=main,maxpri=10]
     java.lang.ThreadGroup[name=main,maxpri=10]
     java.lang.ThreadGroup[name=main,maxpri=10]
     false
     java.lang.ThreadGroup[name=main,maxpri=10]
     [Ljava.lang.StackTraceElement;@3127c164
 after sleep(1500) Is held by Current Thread - true
task name - Job1 work done

Next TopicJava ReentrantLock

← prev next →