java bucket sort

public static int[] bucketSort(int[] a) {
  Queue<Integer>[] buckets = fillBuckets(a);
  int[] sorted = readBuckets(buckets);
  return sorted;
}

public static Queue<Integer>[] fillBuckets(int[] array) {
  if(array.length == 0){
    Queue<Integer>[] r = new Queue[0];
    return r;
  }
  int vmin = array[0];
  int vmax = array[0];
  for(int i = 0; i < array.length; i++){
    if(array[i] > vmax){
      vmax = array[i];
    }
    if(array[i] < vmin){
      vmin = array[i];
    }
  }
  Queue<Integer>[] buckets = new Queue[vmax - vmin + 1];
  for(int i = 0; i < buckets.length; i++){
    buckets[i] = new LinkedList<Integer>();
  }
  for(int i = 0; i < array.length; i++){
    buckets[array[i] - vmin].add(array[i]);
  }
  return buckets;
}

public static int[] readBuckets(Queue<Integer>[] buckets) {
  if(buckets.length == 0){
    int[] e = new int[0];
    return e;
  }
  ArrayList<Integer> a = new ArrayList<Integer>();
  for(int i = 0 ; i < buckets.length; i++){
    while(buckets[i].peek() != null){
      a.add(buckets[i].remove());
    }
  }
  int[] result = new int[a.size()];
  for(int i = 0; i < a.size(); i++){
    result[i] = a.get(i);
  }
  return result;
}