1 /* 2 * Copyright (c) 2010, 2012 Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.util.function; 26 27 import java.util.Objects; 28 29 /** 30 * Apply a function to the input object yielding an appropriate result object. A 31 * function may variously provide a mapping between types, object instances or 32 * keys and values or any other form of transformation upon the input. 33 * 34 * @param <T> the type of input objects to the {@code apply} operation 35 * @param <R> the type of result objects from the {@code apply} operation. May 36 * be the same type as {@code <T>}. 37 * 38 * @since 1.8 39 */ 40 public interface Function<T, R> { 41 42 /** 43 * Yield an appropriate result object for the input object. 44 * 45 * @param t the input object 46 * @return the function result 47 */ 48 public R apply(T t); 49 50 /** 51 * Combine with another function returning a function which performs both 52 * functions. 53 * 54 * @param <V> Type of output objects from the combined function. May be the 55 * same type as {@code <U>}. 56 * @param after An additional function to be applied to the result of this 57 * function. 58 * @return A function which performs both the original function followed by 59 * a second function. 60 */ 61 public default <V > Function<T, V> compose(Function<? super R, ? extends V> after) { 62 Objects.requireNonNull(after); 63 return (T t) -> after.apply(apply(t)); 64 } 65 }