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.List; 23 24 import javax.annotation.Nullable; 25 26 /** An ordering that compares objects according to a given order. */ 27 @GwtCompatible(serializable = true) 28 final class ExplicitOrdering<T> extends Ordering<T> implements Serializable { 29 final ImmutableMap<T, Integer> rankMap; 30 ExplicitOrdering(List<T> valuesInOrder)31 ExplicitOrdering(List<T> valuesInOrder) { 32 this(buildRankMap(valuesInOrder)); 33 } 34 ExplicitOrdering(ImmutableMap<T, Integer> rankMap)35 ExplicitOrdering(ImmutableMap<T, Integer> rankMap) { 36 this.rankMap = rankMap; 37 } 38 compare(T left, T right)39 @Override public int compare(T left, T right) { 40 return rank(left) - rank(right); // safe because both are nonnegative 41 } 42 rank(T value)43 private int rank(T value) { 44 Integer rank = rankMap.get(value); 45 if (rank == null) { 46 throw new IncomparableValueException(value); 47 } 48 return rank; 49 } 50 buildRankMap( List<T> valuesInOrder)51 private static <T> ImmutableMap<T, Integer> buildRankMap( 52 List<T> valuesInOrder) { 53 ImmutableMap.Builder<T, Integer> builder = ImmutableMap.builder(); 54 int rank = 0; 55 for (T value : valuesInOrder) { 56 builder.put(value, rank++); 57 } 58 return builder.build(); 59 } 60 equals(@ullable Object object)61 @Override public boolean equals(@Nullable Object object) { 62 if (object instanceof ExplicitOrdering) { 63 ExplicitOrdering<?> that = (ExplicitOrdering<?>) object; 64 return this.rankMap.equals(that.rankMap); 65 } 66 return false; 67 } 68 hashCode()69 @Override public int hashCode() { 70 return rankMap.hashCode(); 71 } 72 toString()73 @Override public String toString() { 74 return "Ordering.explicit(" + rankMap.keySet() + ")"; 75 } 76 77 private static final long serialVersionUID = 0; 78 } 79