1 /* 2 * Copyright (C) 2007 Google Inc. 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 import com.google.common.base.Function; 21 import com.google.common.base.Objects; 22 import static com.google.common.base.Preconditions.checkNotNull; 23 24 import java.io.Serializable; 25 26 import javax.annotation.Nullable; 27 28 /** 29 * An ordering that orders elements by applying an order to the result of a 30 * function on those elements. 31 */ 32 @GwtCompatible(serializable = true) 33 final class ByFunctionOrdering<F, T> 34 extends Ordering<F> implements Serializable { 35 final Function<F, ? extends T> function; 36 final Ordering<T> ordering; 37 ByFunctionOrdering( Function<F, ? extends T> function, Ordering<T> ordering)38 ByFunctionOrdering( 39 Function<F, ? extends T> function, Ordering<T> ordering) { 40 this.function = checkNotNull(function); 41 this.ordering = checkNotNull(ordering); 42 } 43 compare(F left, F right)44 public int compare(F left, F right) { 45 return ordering.compare(function.apply(left), function.apply(right)); 46 } 47 equals(@ullable Object object)48 @Override public boolean equals(@Nullable Object object) { 49 if (object == this) { 50 return true; 51 } 52 if (object instanceof ByFunctionOrdering) { 53 ByFunctionOrdering<?, ?> that = (ByFunctionOrdering<?, ?>) object; 54 return this.function.equals(that.function) 55 && this.ordering.equals(that.ordering); 56 } 57 return false; 58 } 59 hashCode()60 @Override public int hashCode() { 61 return Objects.hashCode(function, ordering); 62 } 63 toString()64 @Override public String toString() { 65 return ordering + ".onResultOf(" + function + ")"; 66 } 67 68 private static final long serialVersionUID = 0; 69 } 70