1 public static Object[] mergeSort(Object[] o) { 2     o = o.clone(); 3     mergeSort(o, 0, o.length - 1); 4     return o; 5 } 6  7 private static void mergeSort(Object[] o, int l, int r) { 8     if (r > l) { 9         int mid = (l + r) >>> 1;10         mergeSort(o, l, mid);11         mergeSort(o, mid + 1, r);12         merge(o, l, mid, r);13     }14 }15 16 @SuppressWarnings({ "unchecked", "rawtypes" })17 private static void merge(Object[] o, int l, int mid, int r) {18     Object[] temp = new Object[o.length];19     int lp = l;20     int rp = mid + 1;21     int tp = l;22     while (lp <= mid && rp <= r) {23         Comparable c = (Comparable) o[lp];24         if (c.compareTo(o[rp]) <= 0)25             temp[tp++] = o[lp++];26         else27             temp[tp++] = o[rp++];28     }29     while (lp <= mid)30         temp[tp++] = o[lp++];31     while (rp <= r)32         temp[tp++] = o[rp++];33     while (l <= r)34         o[l] = temp[l++];35 }

 1 public static void loopMergeSort(Object[] array) { 2     int len=array.length; 3     for(int step=1; step<len; step<<=1){ 4         int s2 = step<<1; 5         for(int i=0; i<len; i+=s2){ 6             int r=i+s2-1; 7             int mid=(i+r)>>>1; 8             if(mid>=len) 9                 mid=len-1;10             if(r>=len)11                 r=len-1;12             merge(array, i, mid, r);13         }14         15     }16 }