Java 7 sorting “optimisation”

Question

In Java6 both quicksort and mergesort were used in Arrays#sort, for primitive and object arrays respectively. In Java7 these have both changed, to DualPivotQuickso

Answer 1

I wrote 2 methods test1 and test2 and add the main part of the compiled byte code (Java 1.6 on Snow Leopard) as comment:

    /*
     *     14  iload_1 [b]      -> load value from address 1 to sack
     *     15  iastore          -> store value from stack into int array
     *     16  iinc 3 1 [i]     -> int increment value of address 3
     *     19  iinc 3 1 [i]     -> int increment value of address 3
     */
    public void test1() {
        int b = 0;
        int a[] = new int[10];
        for (int i=0; i<10; i++) {
            a[i] = b; 
            i++;
        }
    }

    /*
     *     14  iinc 3 1 [i]     -> increment value of address 3
     *     17  iload_1 [b]      -> load value from address 1 to stack
     *     18  iastore          -> store value from stack into int array
     *     19  iinc 3 1 [i]     -> increment value of address 3 
     */
    public void test2() {
        int b = 0;
        int a[] = new int[10];
        for (int i=0; i<10; i++) {
            a[i++] = b;
        }
    }

The order of the inc ops is different. But the operation sum of both methods test1 and test2 are equal! So the byte codes performance should be the same, too.