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streamsupport is a backport of the Java 8 java.util.function (functional interfaces) and java.util.stream (streams) API for Java 6 / 7 and Android developers

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/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java8.util.function;

import java8.util.Objects;

/**
 * A place for static default implementations of the new Java 8
 * default interface methods and static interface methods in the
 * {@link BiFunction} interface. 
 */
public final class BiFunctions {
    /**
     * Returns a composed function that first applies the {@code this_} function to
     * its inputs, and then applies the {@code after} function to the result.
     * If evaluation of either function throws an exception, it is relayed to
     * the caller of the composed function.
     * 
     * @param  the type of the result of the {@code this_} function and the type of the input of the {@code after} function.
     * @param  the type of the first argument to the {@code this_} function
     * @param  the type of the second argument to the {@code this_} function
     * @param  the type of output of the {@code after} function, and of the
     *           composed function
     * @param this_ the {@code BiFunction} to be applied first.
     * @param after the function to apply after the {@code this_} function is applied
     * @return a composed function that first applies the {@code this_} function and then
     * applies the {@code after} function
     * @throws NullPointerException if {@code this_} is null
     * @throws NullPointerException if after is null
     */
    public static  BiFunction andThen(BiFunction this_, Function after) {
        Objects.requireNonNull(this_);
        Objects.requireNonNull(after);
        return (T t, U u) -> after.apply(this_.apply(t, u));
    }

    private BiFunctions() {
    }
}