FixedThreadPool

       
 ExecutorService es = Executors.newFixedThreadPool(2);
 es.execute(new MyThread(cdl, "A"));
 es.execute(new MyThread(cdl, "B"));
 es.execute(new MyThread(cdl, "C"));
 es.execute(new MyThread(cdl, "D"));

public class SimpExec {
    public static void main(String args[]){
        CountDownLatch cdl = new CountDownLatch(5);
        CountDownLatch cdl2 = new CountDownLatch(5);
        CountDownLatch cdl3= new CountDownLatch(5);
        CountDownLatch cdl4 = new CountDownLatch(5);
        ExecutorService es = Executors.newFixedThreadPool(2);
 
        System.out.println("Запуск потоков");
 
        es.execute(new MyThread(cdl, "A"));
        es.execute(new MyThread(cdl, "B"));
        es.execute(new MyThread(cdl, "C"));
        es.execute(new MyThread(cdl, "D"));
 
        try {
            cdl.await();
            cdl2.await();
            cdl3.await();
            cdl4.await();
        } catch (InterruptedException exc){
            System.out.println(exc);
        }
 
        es.shutdown();
        System.out.println("Завершение потоков");
    }
    static class MyThread implements Runnable {
        String name;
        CountDownLatch latch;
 
        MyThread(CountDownLatch c, String n) {
            latch = c;
            name = n;
 
            new Thread(this);
        }
 
        public void run() {
 
            for (int i = 0; i < 5; i++) {
                System.out.println(name + " : " + i);
                latch.countDown();
            }
        }
    }
}

 es.execute(new MyThread(cdl, "A"));
 es.execute(new MyThread(cdl, "B"));
 es.execute(new MyThread(cdl, "C"));
 es.execute(new MyThread(cdl, "D"));