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 import java.util.Comparator; 29 30 /** 31 * An operation upon two operands yielding a result. This is a specialization of 32 * {@code BiFunction} where the operands and the result are all of the same type. 33 * 34 * @param <T> the type of operands to {@code apply} and of the result 35 * 36 * @see BiFunction 37 * @since 1.8 38 */ 39 @FunctionalInterface 40 public interface BinaryOperator<T> extends BiFunction<T,T,T> { 41 /** 42 * Returns a {@link BinaryOperator} which returns the lesser of two elements 43 * according to the specified {@code Comparator} 44 * 45 * @param <T> the type of values to be compared and returned 46 * @param comparator a {@code Comparator} for comparing the two values 47 * @return a {@code BinaryOperator} which returns the lesser of its operands, 48 * according to the supplied {@code Comparator} 49 * @throws NullPointerException if the argument is null 50 */ 51 public static<T> BinaryOperator<T> minBy(Comparator<? super T> comparator) { 52 Objects.requireNonNull(comparator); 53 return (a, b) -> comparator.compare(a, b) <= 0 ? a : b; 54 } 55 56 /** 57 * Returns a {@link BinaryOperator} which returns the greater of two elements 58 * according to the specified {@code Comparator} 59 * 60 * @param <T> the type of values to be compared and returned 61 * @param comparator a {@code Comparator} for comparing the two values 62 * @return a {@code BinaryOperator} which returns the greater of its operands, 63 * according to the supplied {@code Comparator} 64 * @throws NullPointerException if the argument is null 65 */ 66 public static<T> BinaryOperator<T> maxBy(Comparator<? super T> comparator) { 67 Objects.requireNonNull(comparator); 68 return (a, b) -> comparator.compare(a, b) >= 0 ? a : b; 69 } 70 }