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 static com.google.common.base.Preconditions.checkNotNull; 20 21 import com.google.common.annotations.GwtCompatible; 22 23 import java.io.Serializable; 24 import java.util.Iterator; 25 26 import javax.annotation.Nullable; 27 28 /** An ordering that uses the reverse of a given order. */ 29 @GwtCompatible(serializable = true) 30 final class ReverseOrdering<T> extends Ordering<T> implements Serializable { 31 final Ordering<? super T> forwardOrder; 32 ReverseOrdering(Ordering<? super T> forwardOrder)33 ReverseOrdering(Ordering<? super T> forwardOrder) { 34 this.forwardOrder = checkNotNull(forwardOrder); 35 } 36 compare(T a, T b)37 @Override public int compare(T a, T b) { 38 return forwardOrder.compare(b, a); 39 } 40 41 @SuppressWarnings("unchecked") // how to explain? reverse()42 @Override public <S extends T> Ordering<S> reverse() { 43 return (Ordering<S>) forwardOrder; 44 } 45 46 // Override the min/max methods to "hoist" delegation outside loops 47 min(E a, E b)48 @Override public <E extends T> E min(E a, E b) { 49 return forwardOrder.max(a, b); 50 } 51 min(E a, E b, E c, E... rest)52 @Override public <E extends T> E min(E a, E b, E c, E... rest) { 53 return forwardOrder.max(a, b, c, rest); 54 } 55 min(Iterator<E> iterator)56 @Override public <E extends T> E min(Iterator<E> iterator) { 57 return forwardOrder.max(iterator); 58 } 59 min(Iterable<E> iterable)60 @Override public <E extends T> E min(Iterable<E> iterable) { 61 return forwardOrder.max(iterable); 62 } 63 max(E a, E b)64 @Override public <E extends T> E max(E a, E b) { 65 return forwardOrder.min(a, b); 66 } 67 max(E a, E b, E c, E... rest)68 @Override public <E extends T> E max(E a, E b, E c, E... rest) { 69 return forwardOrder.min(a, b, c, rest); 70 } 71 max(Iterator<E> iterator)72 @Override public <E extends T> E max(Iterator<E> iterator) { 73 return forwardOrder.min(iterator); 74 } 75 max(Iterable<E> iterable)76 @Override public <E extends T> E max(Iterable<E> iterable) { 77 return forwardOrder.min(iterable); 78 } 79 hashCode()80 @Override public int hashCode() { 81 return -forwardOrder.hashCode(); 82 } 83 equals(@ullable Object object)84 @Override public boolean equals(@Nullable Object object) { 85 if (object == this) { 86 return true; 87 } 88 if (object instanceof ReverseOrdering) { 89 ReverseOrdering<?> that = (ReverseOrdering<?>) object; 90 return this.forwardOrder.equals(that.forwardOrder); 91 } 92 return false; 93 } 94 toString()95 @Override public String toString() { 96 return forwardOrder + ".reverse()"; 97 } 98 99 private static final long serialVersionUID = 0; 100 } 101