Re: performance of HashSet with strings and integers

Hi,

I thought of replacing strings with integers in some code I wrote,
because I believed it would benefit performance. But before doing so,
I made a small test class:

public class testStringSetVsIntSet {
    public static void main(String[] args) {
        long time;
        boolean b;
        Set set;

        Integer I1 = new Integer(100), I2 = new Integer(500);

        set = new HashSet();
        set.add(I1);
        set.add(900);

        time = System.currentTimeMillis();
        for (int i=0; i<50000000; i++) {
            b = set.contains(I1);
            b = set.contains(I2);
        }

        time = System.currentTimeMillis() - time;
        System.out.println("Time 1: " + time);

        String headStr = "Head";
        String agentStr = "Agent";
        String qualifStr = "Qualif";

        set = new HashSet();
        set.add(headStr);
        set.add(agentStr);

        time = System.currentTimeMillis();
        for (int i=0; i<50000000; i++) {
            b = set.contains(headStr);
            b = set.contains(qualifStr);
        }

        time = System.currentTimeMillis() - time;
        System.out.println("Time 2: " + time);
       }
}

But to my surprise, the second loop with the strings appeared to be
twice as fast as the first one with the integers! (first loop 3
seconds, second 1.5 seconds)
I didn't expect this because calculating the hashcode for a string is
normally slower than for an integer (every string character is taken
into account) and I thought the "equals" method for a string should be
slower than for an Integer as well.
Can anybody explain this to me?