java实现快速排序

public static void main(String[] args) {
        Comparable[] a = {23, 3, 4, 5, 30, 2};
        sort(a, 0, 5);
        show(a);
    }
    //algorith
    public static void sort(Comparable[] a, int lo, int hi){
        if (hi <= lo) return;
        int j = partition(a, lo, hi);
        sort(a, lo, j-1);
        sort(a, j + 1, hi);
    }
    private static int partition(Comparable[] a, int lo, int hi){
        int i = lo, j = hi + 1;
        Comparable v= a[lo];
        while (true){
            while (less(a[++i],v)) if (i==hi) break;
            while (less(v,a[--j])) if (j==lo) break;
            if (i >= j) break;
            exch(a, i, j);
        }
        exch(a, lo, j);
        return j;
    }
    private static boolean less(Comparable v, Comparable w){ return v.compareTo(w) < 0;}
    private static void exch(Comparable[] a, int i, int j){
        Comparable t = a[i]; a[i] = a[j]; a[j] = t;
    }
    private static void show(Comparable[] a){
        for (int i = 0; i < a.length; i++)
            System.out.print(a[i] + " ");
        System.out.println();
    }
    public static boolean isSorted(Comparable[] a){
        for (int i = 1; i < a.length; i++)
            if (less(a[i], a[i-1]))
                return false;
        return true;
    }