Java计算程序运行时间

Thread js_time = new Thread(new PP());
js_time.start();

//执行程序

js_time.stop();

class PP implements Runnable {
	public void run() {
		int i = 0;
		while (true) {
			try {
				Thread.sleep(2000);//睡眠2秒
				i = i + 2;
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println("正在处理......已使用" + i + "秒");
		}
	}
}

int t1 = (int) System.currentTimeMillis();

//执行程序

int t2 = (int) System.currentTimeMillis();
System.out.println("已完成，耗时：" + Integer.toString(t2 - t1) + "毫秒");