写一个小程序，用来计算它包含的代码所需的耗时。虽然简单，测试代码是否耗时还是有点用的，不用重新写嘛~

import java.util.Date;import java.util.concurrent.TimeUnit;public class TimeLag {        private Date start;    private Date end;        public TimeLag() {        start = new Date();    }        public String cost() {        end = new Date();        long c = end.getTime() - start.getTime();                String s = new StringBuffer().append("cost ").append(c).append(" milliseconds (").append(c / 1000).append(" seconds).").toString();        return s;    }        public static void main(String[] args) throws InterruptedException {        TimeLag t = new TimeLag();        TimeUnit.SECONDS.sleep(2);        System.out.println(t.cost());    }}