Java ThreadPoolExecutor execute() Method

The execute() method of ThreadPoolExecutor class executes the given task sometime in the future. The task may execute in a new thread or an existing pooled thread. If the task is not submitted to the pool due to any reason, then the task is handled by the current RejectedExecutionHandler.

Syntax

Parameter

command - the task to execute

Returns

Does not return value.

Throws

RejectedExecutionException - at the discretion of RejectedExecutionHandler, if the task cannot be accepted for execution

NullPointerException - if the command is null

Example 1

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.lang.Thread;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ThreadPoolExecutorexecuteExample1  {
  public static void main(String[] args) {
    Task task1 = new Task("t1");
    Task task2 = new Task("t2");
    Task task3 = new Task("t3");
    System.out.println("Starting threads");
    ThreadPoolExecutor tExecutor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
    tExecutor.execute(task1); // start task1
    tExecutor.execute(task2); // start task2
    tExecutor.execute(task3); // start task3
    tExecutor.shutdown(); // shutdown worker threads
    System.out.println("Threads started, main ends\n");
  }
}
class Task implements Runnable {
  private final int sleepTime;
  private final String threadName;
  public Task(String name) {
    threadName = name;
    sleepTime = 1000;
  }
  public void run() {
      System.out.printf("%s going to sleep for %d milliseconds.\n", threadName, sleepTime);
      try {
          Thread.sleep(sleepTime); // put thread to sleep
      } catch (InterruptedException ex) {
          Logger.getLogger(Task.class.getName()).log(Level.SEVERE, null, ex);
      }
    System.out.printf("%s done sleeping\n", threadName);
  }
}

Test it Now

Output:

Starting threads
t2 going to sleep for 1000 milliseconds.
t1 going to sleep for 1000 milliseconds.
t3 going to sleep for 1000 milliseconds.
Threads started, main ends
t2 done sleeping
t3 done sleeping
t1 done sleeping

Example 2

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.lang.Thread;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ThreadPoolExecutorexecuteExample2  {
                public static void main(String[] args) {
                                  Task1 task1 = new Task1("t1");
                                  System.out.println("Starting threads");
                                  ThreadPoolExecutor tExecutor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
                                  tExecutor.execute(task1); // start task1
                                  tExecutor.shutdown(); // shutdown worker threads
                                  System.out.println("Threads started, main ends\n");
                                           }
                                    }
class Task1 implements Runnable {
 private final String threadName;
                   public Task1(String threadName) {
                                            this.threadName = threadName;
                                            }
 @Override
      public void run() {
            for(int i=0 ; i<=10;i++)
                        {
                           if(i<5)
                              {
                                try {
                                     System.out.println("Thread sleeping for 1000 i=" +i);
                                     Thread.sleep(1000);
                                   } catch (InterruptedException ex) {
                                  Logger.getLogger(Task1.class.getName()).log(Level.SEVERE, null, ex);
                                  }
                               }
                           else  {
                                  System.out.println(" now  i > 5 :");
                                   break;
                                }
                        }
                        }
}

Test it Now

Output:

Starting threads
Threads started, main ends
Thread sleeping for 1000 i=0
Thread sleeping for 1000 i=1
Thread sleeping for 1000 i=2
Thread sleeping for 1000 i=3
Thread sleeping for 1000 i=4
 now  i > 5 :

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