/* * Copyright © 2016 Cask Data, Inc. * Portions copyright (C) 2007 The Guava Authors * Derived from the Google Guava Project * * 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 co.cask.cdap.internal.guava.reflect; import java.util.Objects; import javax.annotation.Nullable; /** * Determines an output value based on an input value. * * @param <F> input type * @param <T> output type */ 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#equals * Objects.equals}{@code (a, b)} implies that {@code Objects.equals(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); }