1607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller/*
2607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
3607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
5607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * This code is free software; you can redistribute it and/or modify it
6607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * under the terms of the GNU General Public License version 2 only, as
7607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * published by the Free Software Foundation.  Oracle designates this
8607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * particular file as subject to the "Classpath" exception as provided
9607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * by Oracle in the LICENSE file that accompanied this code.
10607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
11607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * This code is distributed in the hope that it will be useful, but WITHOUT
12607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * version 2 for more details (a copy is included in the LICENSE file that
15607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * accompanied this code).
16607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
17607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * You should have received a copy of the GNU General Public License version
18607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * 2 along with this work; if not, write to the Free Software Foundation,
19607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
21607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * or visit www.oracle.com if you need additional information or have any
23607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * questions.
24607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller */
25607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fullerpackage java.util.function;
26607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller
27607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fullerimport java.util.Objects;
28607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fullerimport java.util.Comparator;
29607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller
30607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller/**
31607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * Represents an operation upon two operands of the same type, producing a result
32607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * of the same type as the operands.  This is a specialization of
33607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * {@link BiFunction} for the case where the operands and the result are all of
34607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * the same type.
35607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
36607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * <p>This is a <a href="package-summary.html">functional interface</a>
37607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * whose functional method is {@link #apply(Object, Object)}.
38607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
39607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * @param <T> the type of the operands and result of the operator
40607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller *
41607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * @see BiFunction
42607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * @see UnaryOperator
43607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller * @since 1.8
44607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller */
45607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller@FunctionalInterface
46607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fullerpublic interface BinaryOperator<T> extends BiFunction<T,T,T> {
47607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller    /**
48607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * Returns a {@link BinaryOperator} which returns the lesser of two elements
49607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * according to the specified {@code Comparator}.
50607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     *
51607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @param <T> the type of the input arguments of the comparator
52607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @param comparator a {@code Comparator} for comparing the two values
53607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @return a {@code BinaryOperator} which returns the lesser of its operands,
54607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     *         according to the supplied {@code Comparator}
55607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @throws NullPointerException if the argument is null
56607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     */
57607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller    public static <T> BinaryOperator<T> minBy(Comparator<? super T> comparator) {
58607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller        Objects.requireNonNull(comparator);
59607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller        return (a, b) -> comparator.compare(a, b) <= 0 ? a : b;
60607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller    }
61607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller
62607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller    /**
63607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * Returns a {@link BinaryOperator} which returns the greater of two elements
64607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * according to the specified {@code Comparator}.
65607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     *
66607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @param <T> the type of the input arguments of the comparator
67607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @param comparator a {@code Comparator} for comparing the two values
68607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @return a {@code BinaryOperator} which returns the greater of its operands,
69607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     *         according to the supplied {@code Comparator}
70607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     * @throws NullPointerException if the argument is null
71607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller     */
72607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller    public static <T> BinaryOperator<T> maxBy(Comparator<? super T> comparator) {
73607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller        Objects.requireNonNull(comparator);
74607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller        return (a, b) -> comparator.compare(a, b) >= 0 ? a : b;
75607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller    }
76607050af5a16c46ae53ff4d2c3f47b4ef694b559Neil Fuller}
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