jars/icu4j-4_8_1_1/main/classes/core/src/com/ibm/icu/impl/IterableComparator.java

   1 /*
   2  ************************************************************************************
   3  * Copyright (C) 2007-2010, Google Inc, International Business Machines Corporation *
   4  * and others. All Rights Reserved.                                                 *
   5  ************************************************************************************
   6  */
   7 package com.ibm.icu.impl;
   8
   9 import java.util.Comparator;
  10 import java.util.Iterator;
  11
  12 public class IterableComparator<T> implements Comparator<Iterable<T>> {
  13     private final Comparator<T> comparator;
  14     private final int shorterFirst; // = 1 for shorter first, -1 otherwise
  15
  16     public IterableComparator() {
  17         this(null, true);
  18     }
  19
  20     public IterableComparator(Comparator<T> comparator) {
  21         this(comparator, true);
  22     }
  23
  24     public IterableComparator(Comparator<T> comparator, boolean shorterFirst) {
  25         this.comparator = comparator;
  26         this.shorterFirst = shorterFirst ? 1 : -1;
  27     }
  28
  29     public int compare(Iterable<T> a, Iterable<T> b) {
  30         if (a == null) {
  31             return b == null ? 0 : -shorterFirst;
  32         } else if (b == null) {
  33             return shorterFirst;
  34         }
  35         Iterator<T> ai = a.iterator();
  36         Iterator<T> bi = b.iterator();
  37         while (true) {
  38             if (!ai.hasNext()) {
  39                 return bi.hasNext() ? -shorterFirst : 0;
  40             }
  41             if (!bi.hasNext()) {
  42                 return shorterFirst;
  43             }
  44             T aItem = ai.next();
  45             T bItem = bi.next();
  46             @SuppressWarnings("unchecked")
  47             int result = comparator != null ? comparator.compare(aItem, bItem) : ((Comparable<T>)aItem).compareTo(bItem);
  48             if (result != 0) {
  49                 return result;
  50             }
  51         }
  52     }
  53
  54     @SuppressWarnings("unchecked")
  55     public static <T> int compareIterables(Iterable<T> a, Iterable<T> b) {
  56         return NOCOMPARATOR.compare(a, b);
  57     }
  58
  59     @SuppressWarnings("rawtypes")
  60     private static final IterableComparator NOCOMPARATOR = new IterableComparator();
  61 }