1 /*
   2  * Copyright (c) 2010, 2013, 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 arguments, yielding an appropriate result. This
  31  * is the two-arity specialization of {@link Function}. A function may
  32  * variously provide a mapping between types, object instances or keys and
  33  * values or any other form of transformation upon the input.
  34  *
  35  * @param <T> the type of the first argument to the {@code apply} operation
  36  * @param <U> the type of the second argument to the {@code apply} operation
  37  * @param <R> the type of results returned by the {@code apply} operation
  38  *
  39  * @see Function
  40  * @since 1.8
  41  */
  42 @FunctionalInterface
  43 public interface BiFunction<T, U, R> {
  44 
  45     /**
  46      * Compute the result of applying the function to the input arguments
  47      *
  48      * @param t an input object
  49      * @param u an input object
  50      * @return the function result
  51      */
  52     R apply(T t, U u);
  53 
  54     /**
  55      * Returns a new function which applies this function followed by the
  56      * provided function.  If either function throws an exception, it is relayed
  57      * to the caller.
  58      *
  59      * @param <V> Type of output objects to the combined function. May be the
  60      * same type as {@code <T>}, {@code <U>} or {@code <R>}
  61      * @param after An additional function to be applied after this function is
  62      * applied
  63      * @return A function which performs this function followed by the provided
  64      * function
  65      * @throws NullPointerException if after is null
  66      */
  67     default <V> BiFunction<T, U, V> andThen(Function<? super R, ? extends V> after) {
  68         Objects.requireNonNull(after);
  69         return (T t, U u) -> after.apply(apply(t, u));
  70     }
  71 }