1 /* 2 * Copyright (C) 2007 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.collect; 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 /** 27 * An ordering which sorts iterables by comparing corresponding elements 28 * pairwise. 29 */ 30 @GwtCompatible(serializable = true) 31 final class LexicographicalOrdering<T> 32 extends Ordering<Iterable<T>> implements Serializable { 33 final Ordering<? super T> elementOrder; 34 LexicographicalOrdering(Ordering<? super T> elementOrder)35 LexicographicalOrdering(Ordering<? super T> elementOrder) { 36 this.elementOrder = elementOrder; 37 } 38 compare( Iterable<T> leftIterable, Iterable<T> rightIterable)39 @Override public int compare( 40 Iterable<T> leftIterable, Iterable<T> rightIterable) { 41 Iterator<T> left = leftIterable.iterator(); 42 Iterator<T> right = rightIterable.iterator(); 43 while (left.hasNext()) { 44 if (!right.hasNext()) { 45 return LEFT_IS_GREATER; // because it's longer 46 } 47 int result = elementOrder.compare(left.next(), right.next()); 48 if (result != 0) { 49 return result; 50 } 51 } 52 if (right.hasNext()) { 53 return RIGHT_IS_GREATER; // because it's longer 54 } 55 return 0; 56 } 57 equals(@ullable Object object)58 @Override public boolean equals(@Nullable Object object) { 59 if (object == this) { 60 return true; 61 } 62 if (object instanceof LexicographicalOrdering) { 63 LexicographicalOrdering<?> that = (LexicographicalOrdering<?>) object; 64 return this.elementOrder.equals(that.elementOrder); 65 } 66 return false; 67 } 68 hashCode()69 @Override public int hashCode() { 70 return elementOrder.hashCode() ^ 2075626741; // meaningless 71 } 72 toString()73 @Override public String toString() { 74 return elementOrder + ".lexicographical()"; 75 } 76 77 private static final long serialVersionUID = 0; 78 } 79