Java Test Method Performance

Question

Currently I´m testing the time it takes to execute 2 static Java methods. Both Are 90% identicyl. The difference is one method is using a interface to communicate with a other class. The second method calls the class as given parameter.

There a simple example :

System.out.println(callBackTest());
System.out.println(directCallTest());

Both methods generate new classes. The wierd part is that the first mehtod return a useable duration in ms and the second not. It´s always 1 ms. When I comment out the first call the seconds call return a useable value.

Even wierder is the fact when i run them in a loop and sum the durations. Every first call return a usable value but other just return 1 ms.

for (int i = 0; i < 20; i++) {
        testo t = new testo();
        duration += t.callBackTest();
        System.out.println(duration);
    }
    System.out
            .println("CallBackTest. Took " + (duration / amountTest) + " in average for " + amountTest + " Tests");
    duration = 0;

    for (int i = 0; i < 20; i++) {
        testo t = new testo();
         duration += t.directCallTest();

        System.out.println(duration);
    }
    System.out.println("DirectTest. Took " + (duration / amountTest) + " in average for " + amountTest + " Tests");

To sum Up this loop: 1. [method1] call = ~1300ms 2. [method1] call = ~1301ms 3. [method1] call = ~1302ms 4. [method1] call = ~1303ms ...

1. [method2] call = ~1ms
2. [method2] call = ~2ms
3. [method2] call = ~3ms
4. [method2] call = ~4ms ...

Btw. using the Spring Tool Stuite.

I´m super confused. Anyone a quick idea?