面试题之开两个线程交替输出数字

java 设计一个类，要求两个线程分别交替输出正负整数：

public class printNumber implements Runnable 
{
	private int sign = 1;//1输出正数，-1输出负数

	private static int seg = 1; //同步信号, 全局常量，所有线程共享

	public printNumber(int sign) {
		this.sign = sign;
	}

	public void run() {
		for (int i=1; i<10; i++)
		{
			try
			{
				printNumber(i);
			}
			catch (Exception e)
			{
				e.printStackTrace();
			}
			
		}
	}

	//同步方法
	private synchronized void printNumber(int i) throws InterruptedException{
		while (seg != sign)
		{
			wait(1000);
		}
		System.out.println(sign * i);
		seg = -1 * seg;
	}

	public static void main(String[] args) {
		printNumber p1 = new printNumber(1);
		printNumber p2 = new printNumber(-1);
		new Thread(p1).start();
		new Thread(p2).start();
	}
}

输出结果：