希尔排序算法的JAVA实现

package Utils.Sort;
/**
*希尔排序，要求待排序的数组必须实现Comparable接口
*/
public class ShellSort implements SortStrategy
{
       private int[] increment;
       /**
       *利用希尔排序算法对数组obj进行排序
       */
       public void sort(Comparable[] obj)
       {
              if (obj == null)
              {
                     throw new NullPointerException("The argument can not be null!");
              }
 
              //初始化步长
              initGap(obj);
 
              //步长依次变化（递减）
              for (int i = increment.length - 1 ;i >= 0 ;i-- )
              {
                     int step = increment[i];                   
                     //由步长位置开始
                     for (int j = step ;j < obj.length ;j++ )