Why byte works slower than int? class instantiation

Question

I have this simple code. If I change int to byte in MyClass then it works 1.5 slower for some reason. Any idea, why?

public class Test {

public static void main(String[] args) {
    double start = System.currentTimeMillis();
    MyClass[] arr = new MyClass[10_000_000];

    for (int i = 0; i < arr.length; i++) {
        arr[i] = new MyClass();
    }

    double end = System.currentTimeMillis();
    System.out.println(end-start);
    }
}
class MyClass {
    final public int pole = 50;
    int eshePole;
}

*If I change int to byte in MyClass then it works 1.5 slower for some reason* .. Are you talking about `pole` and `eshePole` variables? — Vishal K, Jul 05 '13 at 16:57
http://stackoverflow.com/questions/2380696/java-short-integer-long-performance — surfealokesea, Jul 05 '13 at 17:00

score 10 · Accepted Answer · answered Jul 05 '13 at 16:54

It's difficult to trust the results from a test like this, as you haven't done any warmup to allow the JVM to do things like optimise code paths. It's worth looking at articles like:

https://wikis.oracle.com/display/HotSpotInternals/MicroBenchmarks

Your test is also incorrect as System.currentTimeMillis() returns a long, not a double.

Why byte works slower than int? class instantiation

1 Answers1