how to get the ACTUAL execution time of a "method" using Java Reflection?

Question

Hi can anyone help me in this issue

>I am executing a method of a Java class using Java Reflection.Now i want to get the real execution time of a method regardless the time taken by reflection.

class AClass { //method

void abc(){ System.out.println("Hello World"); }

//Now using reflection i am going to invoke this method

AClass aObj=new AClass();

Class _cObj=Class.forName("AClass"); Method _meth_Invoke=cObj.getMethod("abc",null);

//Now hear as u see that if i take time Stamp before executing this (Method.invoke())statement and then after take another time stamp and subtract it(using "System.nanoTime()" ), then i get the TIME of both methods abc()+ invoke() method.And thats the problem that i just want to get know the actual execution time of Method abc().

_meth_Invoke.invoke(aObj,...); }

Kindly guide me i spent a lot of time on surfing but cant fine the right material for it.

Answer 1

Use a profiler to find out how much time the program is spending executing the method. If you're using Oracle's JDK 6 (or newer), you could use JVisualVM which is included with the JDK for profiling.

Start it by entering the command jvisualvm in a command prompt window.

Answer 2

The cost of calling a Method via reflection is typically sub-microsecond. You can benchmark this on your machine to confirm this. If you are trying to benchmark a method which is less than 10 micro-seconds this is very hard to do accurately. If its much more than this I wouldn't worry about it.

Answer 3

You can measure the time it takes to call an empty method (void xyz() {}) via reflection and subtract it from the time you measured calling the abc() method via reflection. This is as accurate as you can get programmatically.

Otherwise you have to use a profiler like JVisualVM.