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 javax.annotation.CheckForNull; 26 import org.checkerframework.checker.nullness.qual.Nullable; 27 28 /** 29 * An ordering that orders elements by applying an order to the result of a function on those 30 * elements. 31 */ 32 @GwtCompatible(serializable = true) 33 @ElementTypesAreNonnullByDefault 34 final class ByFunctionOrdering<F extends @Nullable Object, T extends @Nullable Object> 35 extends Ordering<F> implements Serializable { 36 final Function<F, ? extends T> function; 37 final Ordering<T> ordering; 38 ByFunctionOrdering(Function<F, ? extends T> function, Ordering<T> ordering)39 ByFunctionOrdering(Function<F, ? extends T> function, Ordering<T> ordering) { 40 this.function = checkNotNull(function); 41 this.ordering = checkNotNull(ordering); 42 } 43 44 @Override compare(@arametricNullness F left, @ParametricNullness F right)45 public int compare(@ParametricNullness F left, @ParametricNullness F right) { 46 return ordering.compare(function.apply(left), function.apply(right)); 47 } 48 49 @Override equals(@heckForNull Object object)50 public boolean equals(@CheckForNull Object object) { 51 if (object == this) { 52 return true; 53 } 54 if (object instanceof ByFunctionOrdering) { 55 ByFunctionOrdering<?, ?> that = (ByFunctionOrdering<?, ?>) object; 56 return this.function.equals(that.function) && this.ordering.equals(that.ordering); 57 } 58 return false; 59 } 60 61 @Override hashCode()62 public int hashCode() { 63 return Objects.hashCode(function, ordering); 64 } 65 66 @Override toString()67 public String toString() { 68 return ordering + ".onResultOf(" + function + ")"; 69 } 70 71 private static final long serialVersionUID = 0; 72 } 73