Why does java.util.Arrays.sort(Object[]) use 2 kinds of sorting algorithms?

Question

I found that java.util.Arrays.sort(Object[]) use 2 kinds of sorting algorithms(in JDK 1.6).

pseudocode:

if(array.length<7)
   inserti         


        

Answer 1

It's for speed. The overhead of mergeSort is high enough that for short arrays it would be slower than insertion sort.