Merge sort

 
public class MergeSortArray {
  private long[] theArray;

  private int nElems;

  public MergeSortArray(int max) {
    theArray = new long[max];
    nElems = 0;
  }

  public void insert(long value) {
    theArray[nElems] = value; // insert it
    nElems++; // increment size
  }

  public void display() {
    for (int j = 0; j < nElems; j++)
      System.out.print(theArray[j] + " ");
    System.out.println("");
  }

  public void mergeSort() {
    long[] workSpace = new long[nElems];
    recMergeSort(workSpace, 0, nElems - 1);
  }

  private void recMergeSort(long[] workSpace, int lowerBound, int upperBound) {
    if (lowerBound == upperBound) // if range is 1,
      return; // no use sorting
    else { // find midpoint
      int mid = (lowerBound + upperBound) / 2;
      // sort low half
      recMergeSort(workSpace, lowerBound, mid);
      // sort high half
      recMergeSort(workSpace, mid + 1, upperBound);
      // merge them
      merge(workSpace, lowerBound, mid + 1, upperBound);
    }
  }

  private void merge(long[] workSpace, int lowPtr, int highPtr, int upperBound) {
    int j = 0; // workspace index
    int lowerBound = lowPtr;
    int mid = highPtr - 1;
    int n = upperBound - lowerBound + 1; // # of items

    while (lowPtr <= mid && highPtr <= upperBound)
      if (theArray[lowPtr] < theArray[highPtr])
        workSpace[j++] = theArray[lowPtr++];
      else
        workSpace[j++] = theArray[highPtr++];

    while (lowPtr <= mid)
      workSpace[j++] = theArray[lowPtr++];

    while (highPtr <= upperBound)
      workSpace[j++] = theArray[highPtr++];

    for (j = 0; j < n; j++)
      theArray[lowerBound + j] = workSpace[j];
  }

  public static void main(String[] args) {
    int maxSize = 100; // array size
    MergeSortArray arr = new MergeSortArray(maxSize); // create the array

    arr.insert(14);
    arr.insert(21);
    arr.insert(43);
    arr.insert(50);
    arr.insert(62);
    arr.insert(75);
    arr.insert(14);
    arr.insert(2);
    arr.insert(39);
    arr.insert(5);
    arr.insert(608);
    arr.insert(36);

    arr.display();

    arr.mergeSort();

    arr.display();
  }
}