1 /* 2 * Copyright (c) 2010, 2011, 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 objects yielding an appropriate result object. 31 * A 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 <R> the type of output objects from {@code apply} operation. 35 * @param <T> the type of input objects provided to the {@code apply} operation. 36 * @param <U> the type of input objects provided to the {@code apply} operation. 37 */ 38 public interface BiFunction<T, U, R> { 39 40 /** 41 * Map the provided input objects to an appropriate output object. 42 * 43 * @param t an input object 44 * @param u an input object 45 * @return the function result 46 */ 47 R apply(T t, U u); 48 49 /** 50 * Combine with another function producing a function which performs both 51 * operations. 52 * 53 * @param <W> Type of output objects from the combined function. May be the 54 * same type as {@code <U>}. 55 * @param after An additional function to be applied to the result of this 56 * function. 57 * @return A function which performs both the original function followed by 58 * a second function. 59 */ 60 public default <W> BiFunction<T, U, W> compose(Function<? super R, ? extends W> after) { 61 Objects.requireNonNull(after); 62 return (T t, U u) -> after.apply(apply(t, u)); 63 } 64 }