package org.junit.runner.manipulation;
   
   import java.util.Comparator;
   
   import org.junit.runner.Description;
   
   /**
    * A <code>Sorter</code> orders tests. In general you will not need
    * to use a <code>Sorter</code> directly. Instead, use {@link org.junit.runner.Request#sortWith(Comparator)}.
   *
   * @since 4.0
   */
  public class Sorter implements Comparator<Description> {
      /**
       * NULL is a <code>Sorter</code> that leaves elements in an undefined order
       */
      public static final Sorter NULL = new Sorter(new Comparator<Description>() {
          public int compare(Description o1, Description o2) {
              return 0;
          }
      });
  
      private final Comparator<Description> comparator;
  
      /**
       * Creates a <code>Sorter</code> that uses <code>comparator</code>
       * to sort tests
       *
       * @param comparator the {@link Comparator} to use when sorting tests
       */
      public Sorter(Comparator<Description> comparator) {
          this.comparator = comparator;
      }
  
      /**
       * Sorts the test in <code>runner</code> using <code>comparator</code>
       */
      public void apply(Object object) {
          if (object instanceof Sortable) {
              Sortable sortable = (Sortable) object;
              sortable.sort(this);
          }
      }
  
      public int compare(Description o1, Description o2) {
          return comparator.compare(o1, o2);
      }
  }