| /* |
| * Copyright (C) 2007 The Guava Authors |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.google.common.base; |
| |
| import com.google.common.annotations.GwtCompatible; |
| |
| import javax.annotation.Nullable; |
| |
| /** |
| * Determines an output value based on an input value. |
| * |
| * <p>The {@link Functions} class provides common functions and related utilites. |
| * |
| * <p>See the Guava User Guide article on <a href= |
| * "http://code.google.com/p/guava-libraries/wiki/FunctionalExplained">the use of {@code |
| * Function}</a>. |
| * |
| * @author Kevin Bourrillion |
| * @since 2.0 (imported from Google Collections Library) |
| */ |
| @GwtCompatible |
| public interface Function<F, T> { |
| /** |
| * Returns the result of applying this function to {@code input}. This method is <i>generally |
| * expected</i>, but not absolutely required, to have the following properties: |
| * |
| * <ul> |
| * <li>Its execution does not cause any observable side effects. |
| * <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal |
| * Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a), |
| * function.apply(b))}. |
| * </ul> |
| * |
| * @throws NullPointerException if {@code input} is null and this function does not accept null |
| * arguments |
| */ |
| @Nullable T apply(@Nullable F input); |
| |
| /** |
| * Indicates whether another object is equal to this function. |
| * |
| * <p>Most implementations will have no reason to override the behavior of {@link Object#equals}. |
| * However, an implementation may also choose to return {@code true} whenever {@code object} is a |
| * {@link Function} that it considers <i>interchangeable</i> with this one. "Interchangeable" |
| * <i>typically</i> means that {@code Objects.equal(this.apply(f), that.apply(f))} is true for all |
| * {@code f} of type {@code F}. Note that a {@code false} result from this method does not imply |
| * that the functions are known <i>not</i> to be interchangeable. |
| */ |
| @Override |
| boolean equals(@Nullable Object object); |
| } |