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      1 //  2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html#License
      3 /*
      4  ************************************************************************************
      5  * Copyright (C) 2007-2015, Google Inc, International Business Machines Corporation
      6  * and others. All Rights Reserved.
      7  ************************************************************************************
      8  */
      9 package com.ibm.icu.impl;
     10 
     11 import java.util.Comparator;
     12 import java.util.Iterator;
     13 
     14 /**
     15  * TODO: Move to com.ibm.icu.dev.somewhere.
     16  * 2015-sep-03: Not used in ICU but used in CLDR and in UnicodeTools.
     17  */
     18 public class IterableComparator<T> implements Comparator<Iterable<T>> {
     19     private final Comparator<T> comparator;
     20     private final int shorterFirst; // = 1 for shorter first, -1 otherwise
     21 
     22     public IterableComparator() {
     23         this(null, true);
     24     }
     25 
     26     public IterableComparator(Comparator<T> comparator) {
     27         this(comparator, true);
     28     }
     29 
     30     public IterableComparator(Comparator<T> comparator, boolean shorterFirst) {
     31         this.comparator = comparator;
     32         this.shorterFirst = shorterFirst ? 1 : -1;
     33     }
     34 
     35     @Override
     36     public int compare(Iterable<T> a, Iterable<T> b) {
     37         if (a == null) {
     38             return b == null ? 0 : -shorterFirst;
     39         } else if (b == null) {
     40             return shorterFirst;
     41         }
     42         Iterator<T> ai = a.iterator();
     43         Iterator<T> bi = b.iterator();
     44         while (true) {
     45             if (!ai.hasNext()) {
     46                 return bi.hasNext() ? -shorterFirst : 0;
     47             }
     48             if (!bi.hasNext()) {
     49                 return shorterFirst;
     50             }
     51             T aItem = ai.next();
     52             T bItem = bi.next();
     53             @SuppressWarnings("unchecked")
     54             int result = comparator != null ? comparator.compare(aItem, bItem) : ((Comparable<T>)aItem).compareTo(bItem);
     55             if (result != 0) {
     56                 return result;
     57             }
     58         }
     59     }
     60 
     61     @SuppressWarnings("unchecked")
     62     public static <T> int compareIterables(Iterable<T> a, Iterable<T> b) {
     63         return NOCOMPARATOR.compare(a, b);
     64     }
     65 
     66     @SuppressWarnings("rawtypes")
     67     private static final IterableComparator NOCOMPARATOR = new IterableComparator();
     68 }