Merge Sort

public static void mergeSort(double [] array, int first, int last) {

        if (first < last) {
            int middle = (first+last) / 2; // Get middle element of array
            mergeSort(array, first, middle); // Sort left side of the array
            mergeSort(array, middle + 1, last); // Sort right side of the array
            merge(array, first, middle, last); // Combine both sides
        }
    }

public static void merge(double [] array,int first, int middle, int last) {

        // Copy both parts into the helper array
          double [] temp = new double [array.length];
        for (int i = first; i <= last; i++) {
          temp[i] = array[i];
        }

        int i = first;
        int j = middle + 1;
        int k = first;
        // Copy the smallest values from left or right side back into original array

        while (i <= middle && j <= last) {
          if (temp[i] <= temp[j]) {
            array[k] = temp[i];
            i++;
          } else {
            array[k] = temp[j];
            j++;
          }
          k++;
        }
        // Copy the rest of the left side of the array back into original array
        while (i <= middle) {
          array[k] = temp[i];
          k++;
          i++;
        }

      }