交替打印数字

package example;

public class TestAB {

    public static void main(String[] args) {
        new TestAB().test();
    }

    public void test() {
        Object obj = new Object();
        new Thread(new Printer(obj)).start();
        new Thread(new Printer(obj)).start();
        new Thread(new Printer(obj)).start();
        new Thread(new Printer(obj)).start();
    }
}

class Printer implements Runnable {
    Object obj;

    public Printer(Object obj) {
        this.obj = obj;
    }

    @Override
    public void run() {
        String name = Thread.currentThread().getName();
        for (int i = 0; i < 100; i++) {
            synchronized (obj) {
                System.err.println(name + ":" + i);
                try {
                    obj.notifyAll();
                    if (i < 99) {
                        obj.wait();
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        }
    }

}