jdk/src/share/classes/java/util/function/BiFunction.java
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8004015: Additional static and instance utils for functional interfaces. 8011010: Spec j.u.f.Predicate doesn't specify NPEs thrown by the SE8's Reference Implementation Reviewed-by: briangoetz, dholmes, chegar
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/*
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 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.  Oracle designates this
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 * particular file as subject to the "Classpath" exception as provided
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 * by Oracle in the LICENSE file that accompanied this code.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 */
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package java.util.function;
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import java.util.Objects;
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/**
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 * Apply a function to the input arguments, yielding an appropriate result. This
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 * is the two-arity specialization of {@link Function}. A function may
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 * variously provide a mapping between types, object instances or keys and
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 * values or any other form of transformation upon the input.
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 *
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 * @param <T> the type of the first argument to the {@code apply} operation
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 * @param <U> the type of the second argument to the {@code apply} operation
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 * @param <R> the type of results returned by the {@code apply} operation
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 *
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 * @see Function
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 * @since 1.8
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 */
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@FunctionalInterface
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public interface BiFunction<T, U, R> {
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    /**
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     * Compute the result of applying the function to the input arguments
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     *
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     * @param t an input object
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     * @param u an input object
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     * @return the function result
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     */
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    R apply(T t, U u);
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    /**
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     * Returns a new function which applies this function followed by the
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     * provided function.  If either function throws an exception, it is relayed
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     * to the caller.
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     *
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     * @param <V> Type of output objects to the combined function. May be the
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     * same type as {@code <T>}, {@code <U>} or {@code <R>}
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     * @param after An additional function to be applied after this function is
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     * applied
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     * @return A function which performs this function followed by the provided
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     * function
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     * @throws NullPointerException if after is null
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     */
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    default <V> BiFunction<T, U, V> andThen(Function<? super R, ? extends V> after) {
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        Objects.requireNonNull(after);
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        return (T t, U u) -> after.apply(apply(t, u));
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    }
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}