jdk1.7的collections.sort(List list)排序问题

System.setProperty("java.util.Arrays.useLegacyMergeSort", "true"); 

public static void sort(Object[] a) {
        if (LegacyMergeSort.userRequested)
            legacyMergeSort(a);
        else
            ComparableTimSort.sort(a);
    }
    /** To be removed in a future release. */
    private static void legacyMergeSort(Object[] a) {
        Object[] aux = a.clone();
        mergeSort(aux, a, 0, a.length, 0);
    }

public static void sort(Object[] a) {
        Object[] aux = (Object[])a.clone();
        mergeSort(aux, a, 0, a.length, 0);
    }