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 import com.google.common.base.Function; 23 import com.google.common.base.Objects; 24 import java.io.Serializable; 25 import org.checkerframework.checker.nullness.compatqual.NullableDecl; 26 27 /** 28 * An ordering that orders elements by applying an order to the result of a function on those 29 * elements. 30 */ 31 @GwtCompatible(serializable = true) 32 final class ByFunctionOrdering<F, T> extends Ordering<F> implements Serializable { 33 final Function<F, ? extends T> function; 34 final Ordering<T> ordering; 35 ByFunctionOrdering(Function<F, ? extends T> function, Ordering<T> ordering)36 ByFunctionOrdering(Function<F, ? extends T> function, Ordering<T> ordering) { 37 this.function = checkNotNull(function); 38 this.ordering = checkNotNull(ordering); 39 } 40 41 @Override compare(F left, F right)42 public int compare(F left, F right) { 43 return ordering.compare(function.apply(left), function.apply(right)); 44 } 45 46 @Override equals(@ullableDecl Object object)47 public boolean equals(@NullableDecl Object object) { 48 if (object == this) { 49 return true; 50 } 51 if (object instanceof ByFunctionOrdering) { 52 ByFunctionOrdering<?, ?> that = (ByFunctionOrdering<?, ?>) object; 53 return this.function.equals(that.function) && this.ordering.equals(that.ordering); 54 } 55 return false; 56 } 57 58 @Override hashCode()59 public int hashCode() { 60 return Objects.hashCode(function, ordering); 61 } 62 63 @Override toString()64 public String toString() { 65 return ordering + ".onResultOf(" + function + ")"; 66 } 67 68 private static final long serialVersionUID = 0; 69 } 70