Home | History | Annotate | Download | only in base 
      1 /*
      2  * Copyright (C) 2011 The Guava Authors
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.common.base;
     18 
     19 import com.google.common.annotations.GwtCompatible;
     20 
     21 import java.io.Serializable;
     22 import java.util.Iterator;
     23 
     24 import javax.annotation.Nullable;
     25 
     26 @GwtCompatible(serializable = true)
     27 final class PairwiseEquivalence<T> extends Equivalence<Iterable<T>>
     28     implements Serializable {
     29 
     30   final Equivalence<? super T> elementEquivalence;
     31 
     32   PairwiseEquivalence(Equivalence<? super T> elementEquivalence) {
     33     this.elementEquivalence = Preconditions.checkNotNull(elementEquivalence);
     34   }
     35 
     36   @Override
     37   protected boolean doEquivalent(Iterable<T> iterableA, Iterable<T> iterableB) {
     38     Iterator<T> iteratorA = iterableA.iterator();
     39     Iterator<T> iteratorB = iterableB.iterator();
     40 
     41     while (iteratorA.hasNext() && iteratorB.hasNext()) {
     42       if (!elementEquivalence.equivalent(iteratorA.next(), iteratorB.next())) {
     43         return false;
     44       }
     45     }
     46 
     47     return !iteratorA.hasNext() && !iteratorB.hasNext();
     48   }
     49 
     50   @Override
     51   protected int doHash(Iterable<T> iterable) {
     52     int hash = 78721;
     53     for (T element : iterable) {
     54       hash = hash * 24943 + elementEquivalence.hash(element);
     55     }
     56     return hash;
     57   }
     58 
     59   @Override
     60   public boolean equals(@Nullable Object object) {
     61     if (object instanceof PairwiseEquivalence) {
     62       PairwiseEquivalence<?> that = (PairwiseEquivalence<?>) object;
     63       return this.elementEquivalence.equals(that.elementEquivalence);
     64     }
     65 
     66     return false;
     67   }
     68 
     69   @Override
     70   public int hashCode() {
     71     return elementEquivalence.hashCode() ^ 0x46a3eb07;
     72   }
     73 
     74   @Override
     75   public String toString() {
     76     return elementEquivalence + ".pairwise()";
     77   }
     78 
     79   private static final long serialVersionUID = 1;
     80 }
     81