Java ReentrantLock isHeldByCurrentThread() Method

The isHeldByCurrentThread() method of ReentrantLock Class checks if the current thread occupies this lock.

Syntax

Parameter

No parameter is passed.

Returns

true if current thread holds this lock and false otherwise

Throws

No Exception is thrown.

Example 1

 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 WorkerClass21 implements Runnable 
 { 
   String nm; 
   ReentrantLock relc; 
   public WorkerClass21(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
        
         { 
        	 Thread t=new Thread();
        	 
        	 for(int i =0 ; i<=5 ; i++)
        	 {
        		if(i>3){        				
        			System.out.println("    "+i+  "  " +t.getPriority());	
        			t.sleep(1500);
        		}
        		if(i<2) {
        			System.out.println("    "+i+  "  " +t.getName());
        			t.sleep(1500);
        		}
        		
        	 }
           
           relc.lock(); 
         }
         
           catch(InterruptedException e) 
           { 
             e.printStackTrace(); 
           } 
           
           System.out.println(" after sleep(1500) Is held by Current Thread - " + relc.isHeldByCurrentThread()); 
           System.out.println("task name - " + nm + " work done"); 
   
           dn = true; 
         } 
          { 
     
       }       
       } 
     } 
      
   } 
  
   
 public class ReentrantLockisHeldByCurrentThreadExample1 
 { 
   static final int Time = 2; 
   public static void main(String[] args) 
   { 
     ReentrantLock rel = new ReentrantLock(); 
     ExecutorService pool = Executors.newFixedThreadPool(Time); 
     Runnable wrk1 = new WorkerClass21(rel, "Job1"); 
     pool.execute(wrk1); 
     pool.shutdown(); 
   } 
 } 

Test it Now

Output:

    0  Thread-0
    1  Thread-0
    4  5
    5  5
 after sleep(1500) Is held by Current Thread - true
task name - Job1 work done

Example 2

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 WorkerClass22 implements Runnable 
{ 
  String nm; 
  ReentrantLock relc; 
  public WorkerClass22(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;
          }
        	  
         
  
          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 ReentrantLockisHeldByCurrentThreadExample2 
{ 
  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 WorkerClass22(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;@6bd19be0
 after sleep(1500) Is held by Current Thread - true
task name - Job1 work done

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