3つのスレッドを起動してABC 10回繰り返し印刷する

package com.study.thread;

/**
 *
 * @author nirvana
 */
public class MyThreadPrinter {

    public static void main(String[] args) {

        MyLock lock = new MyLock();

        Thread a = new Thread(new MyPrinter("A", "B", lock));
        Thread b = new Thread(new MyPrinter("B", "C", lock));
        Thread c = new Thread(new MyPrinter("C", "A", lock));

        a.start();
        b.start();
        c.start();

        lock.setHolder("A");
    }

    static class MyPrinter implements Runnable {

        private String myName;
        private String nextName;
        private final MyLock lock;

        public MyPrinter(String myName, String nextName, MyLock lock) {
            this.myName = myName;
            this.nextName = nextName;
            this.lock = lock;
        }

        public void run() {
            int count = 10;
            while (count > 0) {
                //
                if (lock != null && lock.getHolder() != null && lock.getHolder().equals(myName)) {
                    synchronized (lock) {
                        System.out.println(myName);
                        count--;
                        lock.setHolder(nextName);
                    }
                }

            }
        }
    }

    static class MyLock {

        public MyLock() {
        }
        private String holder;

        public String getHolder() {
            return holder;
        }

        public void setHolder(String holder) {
            this.holder = holder;
        }
    }
}

public class Test implements Runnable {

	private static char[] chars = new char[] { 'A', 'B', 'C' };
	private static Integer index = 0; //  
	private int count = 10;

	public static void main(String[] args) {
		new Thread(new Test()).start();
		new Thread(new Test()).start();
		new Thread(new Test()).start();
	}

	public void run() {
		while (true) {
			synchronized (index) {
				if (index == 3*count)
				{
					return;
				}
				System.out.println(chars[index % 3]);
				index++;
			}
		}
	}
}