11d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert/* 21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2007 The Guava Authors 31d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 41d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Licensed under the Apache License, Version 2.0 (the "License"); 51d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * you may not use this file except in compliance with the License. 61d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * You may obtain a copy of the License at 71d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 81d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * http://www.apache.org/licenses/LICENSE-2.0 91d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Unless required by applicable law or agreed to in writing, software 111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * distributed under the License is distributed on an "AS IS" BASIS, 121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * See the License for the specific language governing permissions and 141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * limitations under the License. 151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertpackage com.google.common.base; 181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.annotations.GwtCompatible; 201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport javax.annotation.Nullable; 221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert/** 241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Determines an output value based on an input value. 251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @author Kevin Bourrillion 271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 (imported from Google Collections Library) 281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@GwtCompatible 301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertpublic interface Function<F, T> { 311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the result of applying this function to {@code input}. This method is <i>generally 331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * expected</i>, but not absolutely required, to have the following properties: 341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <ul> 361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>Its execution does not cause any observable side effects. 371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal 381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a), 391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * function.apply(b))}. 401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * </ul> 411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws NullPointerException if {@code input} is null and this function does not accept null 431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * arguments 441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert T apply(@Nullable F input); 461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Indicates whether another object is equal to this function. 491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Most implementations will have no reason to override the behavior of {@link Object#equals}. 511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * However, an implementation may also choose to return {@code true} whenever {@code object} is a 521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@link Function} that it considers <i>interchangeable</i> with this one. "Interchangeable" 531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <i>typically</i> means that {@code Objects.equal(this.apply(f), that.apply(f))} is true for all 541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code f} of type {@code F}. Note that a {@code false} result from this method does not imply 551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * that the functions are known <i>not</i> to be interchangeable. 561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert boolean equals(@Nullable Object object); 591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert} 60