java.util.concurrent.ExecutorService newFixedThreadPool : If additional tasks are submitted when all threads are active, they will wait in the queue until a thread is available.
Here it is said that "They will wait"..
This does not mean any waiting thread. It means tasks that are submitted will be waiting in a queue for processing.
Submitting the tasks is not a blocking operation. Fixed Thread Pool uses a unbounded queue to hold the submitted tasks.
Task Submitter Thread will not be blocked ...
And the code for copy & paste & run & bye ...
import java.util.concurrent.Executor; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.ThreadPoolExecutor; /** * Created by ssunel on 6/1/2015. */public class TaskSubmitTest { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(5); MyMonitorThread monitor = new MyMonitorThread((ThreadPoolExecutor) executor, 3); Thread monitorThread = new Thread(monitor); monitorThread.start(); for (int i = 0; i < 1000000; i++) { Runnable worker = new WorkerThread("" + i); executor.execute(worker); } System.out.println("All tasks are submitted !!!"); executor.shutdown(); while (!executor.isTerminated()) { } System.out.println("Finished all threads"); } static class WorkerThread implements Runnable { private String command; public WorkerThread(String s){ this.command=s; } @Override public void run() { System.out.println(Thread.currentThread().getName()+" Start. Command = "+command); processCommand(); System.out.println(Thread.currentThread().getName()+" End."); } private void processCommand() { try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } } @Override public String toString(){ return this.command; } } static class MyMonitorThread implements Runnable { private ThreadPoolExecutor executor; private int seconds; private boolean run=true; public MyMonitorThread(ThreadPoolExecutor executor, int delay) { this.executor = executor; this.seconds=delay; } public void shutdown(){ this.run=false; } @Override public void run() { while(run){ System.out.println( String.format("[monitor] [%d/%d] Active: %d, Completed: %d, Task: %d, isShutdown: %s, isTerminated: %s, taskQueueSize: %d", this.executor.getPoolSize(), this.executor.getCorePoolSize(), this.executor.getActiveCount(), this.executor.getCompletedTaskCount(), this.executor.getTaskCount(), this.executor.isShutdown(), this.executor.isTerminated(), this.executor.getQueue().size())); try { Thread.sleep(seconds*1000); } catch (InterruptedException e) { e.printStackTrace(); } } } } }
