////////////////
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){
  return;
 }
 else{
  int mid=(lowerBound+upperBound)/2;
  recMergeSort(workSpace, lowerBound, mid);
  recMergeSort(workSpace, mid+1, upperBound);
  merge(workSpace, lowerBound, mid+1, upperBound);
 }
}
private void merge(long[] workSpace,int lowPtr,int highPtr,int upperBound){
 int j = 0;
 int lowerBound = lowPtr;
 int mid = highPtr - 1;
 int n = upperBound-lowerBound+1;
 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];
 }
}