"mod 4" versus performance "& 3"

I tried to check if it works var & 3faster than var % 4in java (it can also be 2 ^ n - 1 against% 2 ^ n). I made a simple program to calculate the average time needed to perform the calculations, but I get strange results, and I can not conclude. For about 1000 calculations, the average value mod 4takes much longer, but when I try to do about 1,000,000 calculations, both average values ​​are about the same ... I suspect this is due to java optimization of my code, but I'm not sure.

Which of these two operations should be faster and how is it implemented %?

Thank!

EDIT: Here is my test program.

    long startTime, time, sum;
    int iterations = 1000;
    int v;

    sum = 0;
    for(int i = 0; i < iterations; i++)
    {
        startTime = System.nanoTime();
        v = i % 4;
        time = System.nanoTime();
        sum += time-startTime;
    }
    System.out.println("Mod 4 : "+(sum/iterations));

    sum = 0;
    for(int i = 0; i < iterations; i++)
    {
        startTime = System.nanoTime();
        v = i & 3;
        time = System.nanoTime();
        sum += time-startTime;
    }
    System.out.println("& 3 : "+(sum/iterations));

100 130 mod 4 25060 & 3.

1000 1792 mod 4 81 & 3.

1000000 50 , mod 4 .