JAVA多线程，交替打印数字字母

class InsteadPrint {

	public static class PrintABC implements Runnable {

		Object obj = null;

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

		@Override
		public void run() {
			synchronized (obj) {
				char ch = 'A';
				for (int i = 0; i < 26; i++) {
					System.err.println((char) (ch + i));
					try {
						obj.notifyAll();
						obj.wait();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}

		}
	}

	public static class Print123 implements Runnable {

		Object obj = null;

		public Print123(Object obj) {
			this.obj = obj;
		}

		@Override
		public void run() {
			synchronized (obj) {
				for (int i = 0; i < 100; i++) {
					System.err.println(i);
					if (i % 2 == 1) {
						try {
							obj.notifyAll();
							obj.wait();
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
				}

			}
		}
	}

	public void test() {
		Object obj = new Object();
		new Thread(new Print123(obj)).start();
		new Thread(new PrintABC(obj)).start();
	}
}