import java.util.Vector;class Test {private Vector<String> mCache = new Vector<String>();static class Consumer implements Runnable {
        private Test mTestRef;
        Consumer(Test t) {
            mTestRef = t;
        }public void run() {
            try {
                for (; ;) {
                    synchronized (mTestRef) {
                        if (mTestRef.mCache.size() > 0) {
                            String item = mTestRef.mCache.get(0);
                            mTestRef.mCache.remove(0);
                            System.out.println("Consume the item: " + item);
                        } else {
                            mTestRef.wait();
                        }
                    }
                }
            }
            catch (InterruptedException ex) {
            }
        }
    }static class Producer implements Runnable {
        private Test mTestRef;
        private String mProducerId;
        Producer(String id, Test t) {
            mProducerId = id;
            mTestRef = t;
        }public void run() {
            try {
                int i = 0;
                while ((++i)<5) {
                    synchronized (mTestRef) {
                        String item = mProducerId + " #" + i;
                        mTestRef.mCache.add(item);
                        mTestRef.notify();
                    }
                    Thread.sleep(1000);
                }
            }
            catch (InterruptedException ex) {
            }
        }
    }public static void main(String[] args) {
        Test test = new Test();
        Thread consumer = new Thread(new Consumer(test));
        Thread producer1 = new Thread(new Producer("p1", test));
        Thread producer2 = new Thread(new Producer("p2", test));

        producer1.start();
        producer2.start();
        consumer.start();

output is:

Consume the item: p1 #1
Consume the item: p2 #1
Consume the item: p1 #2
Consume the item: p2 #2
Consume the item: p1 #3
Consume the item: p2 #3
Consume the item: p1 #4
Consume the item: p2 #4