3个线程，A，B，C，这三个线程分别只能打印 “a”，“b”，“c”，怎么让这三个线程依次打印“abc"

package com.jbx.thread;

/**
 * 3个线程，A，B，C，这三个线程分别只能打印 “a”，“b”，“c”，怎么让这三个线程依次打印“abc"
 * 
 * @author Administrator
 * 
 */
public class TestJoin {
	public static void main(String[] args) {
		Thread a = new Thread(new AThread());
		Thread b = new Thread(new BThread());
		Thread c = new Thread(new CThread());
		a.start();
		try {
			a.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		b.start();
		try {
			b.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		c.start();
		try {
			c.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		
	}
}

class AThread implements Runnable {

	@Override
	public void run() {

		System.out.println("a");
	}

}

class BThread implements Runnable {

	@Override
	public void run() {

		System.out.println("b");
	}

}

class CThread implements Runnable {

	@Override
	public void run() {

		System.out.println("c");
	}

}

执行结果：
a
b
c

这种方式经测试在main方法中加入循环方法之后无法实现依次输出abcabcabc