java开发实战经典（第二版）P283 9-1

9.1   设计4个线程对象，两个线程执行减操作，两个线程执行加操作。

package book;

class MyThread implements Runnable {
	private int count = 0;

	public void run() {
		while (true) {
			if (Thread.currentThread().getName().startsWith("mul")) {
				count--;
			} else {
				count++;
			}
			System.out.println(count);
			try {
				Thread.sleep(300);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}

		}

	}
}

public class JiOu {
	public static void main(String args[]) {
		MyThread mt = new MyThread();
		Thread mt1 = new Thread(mt, "mul1");
		Thread mt2 = new Thread(mt, "mul2");
		Thread mt3 = new Thread(mt, "add3");
		Thread mt4 = new Thread(mt, "add4");
		mt1.start();
		mt2.start();
		mt3.start();
		mt4.start();
	}
}

运行结果：（部分）

-1
-1
-2
0
1
1
0
1
2
3
2
2
1
2
1
2
2
2
3
1
3
2
3
3
1
1
2
3
4