Java ThreadPoolExecutor beforeExecute() Method

The beforeExecute() method of ThreadPoolExecutor class is invoked before executing the given Runnable in the given thread. This method is invoked by thread t that will execute task r, and may be used to re-initialize ThreadLocals, or to perform logging.

Syntax

Parameters

t - The thread that will run task r

r - The task that will be executed

Return value

Throws

Does not throw the exception.

Example 1

package ThreadPoolExecutorClass;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ThreadPoolExecutorbeforeExecuteExample1  {
	public static void main(String[] args) {
		//Creating a thread pool
		ThreadPoolExecutor obj = new ThreadPoolExecutorbeforeExecuteExample1().new MyThreadExecutor(2, 3, 1,
				TimeUnit.SECONDS, new LinkedBlockingQueue<>());
		
		//execute a runnable
		obj.execute(() -> {
                    System.out.println("In Runnable!");
                });
		obj.shutdown();
	}
class MyThreadExecutor extends ThreadPoolExecutor {
		public MyThreadExecutor(int PoolSize, int maxPoolSize, long keepAliveTime, TimeUnit unit,
				BlockingQueue<Runnable> workQueue) {
			super(PoolSize, maxPoolSize, keepAliveTime, unit, workQueue);
		}
		@Override
		protected void beforeExecute(Thread thread, Runnable run) {
			super.beforeExecute(thread, run);
			System.out.println(thread.getName() + "it will run the task.");
		}
	}
}

Test it Now

Output:

pool-1-thread-1it will run the task.
In Runnable!

Example 2

package ThreadPoolExecutorClass;
import java.util.concurrent.*;
 class MYThreadPoolExecutor2 extends ThreadPoolExecutor {
  public MYThreadPoolExecutor2() { 
       super(1,10,60,TimeUnit.SECONDS,new ArrayBlockingQueue<Runnable>(1000));
   }
   @Override
   protected void beforeExecute(Thread thread, Runnable run){
      super.beforeExecute(thread, run);
         try {
             Object Obj = ((Future<?>) run).get();
             System.out.println(Obj);
         } catch (InterruptedException | ExecutionException e) {  }
       }
     }
  public class ThreadPoolExecutorbeforeExecuteExample2 {
  public static void main(String args[]){
        System.out.println("creating service");
        //ExecutorService service = Executors.newFixedThreadPool(10);
        MYThreadPoolExecutor2 obj2 = new MYThreadPoolExecutor2();
                Future<?> sb = obj2.submit(() -> {
            int a=4, b = 0;
            System.out.println("a and b="+a+":"+b);
            System.out.println("a/b:"+(a/b));
              System.out.println("Thread Name in Runnable after divide by zero:"+Thread.currentThread().getName());
        });
        obj2.shutdown();
    }
}

Test it Now

Output: