put your code after "do something", then the standard output would show how long the code runs to end :
starTime=System.currentTimeMillis();
//do something
endTime=System.currentTimeMillis();
Time=endTime-starTime;
System.out.println(" execution time : " + Time);
思考：
如何更方便地做到对任意代码段实施运行时间的监控？如何不需要重复的复制上述代码？想想Greys，bitman,bittrace.
