rev 7485 : 8009736: Comparator API cleanup
Reviewed-by:
Contributed-by: henry.jen@oracle.com

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
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   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.
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  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).
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  17  * You should have received a copy of the GNU General Public License version
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  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
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  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      * Constructs a {@link BinaryOperator} which returns the lesser of two elements
  43      * according to the specified {@code Comparator}
  44      *
  45      * @param  comparator A {@code Comparator} for comparing the two values
  46      * @return a {@code BinaryOperator} which returns the lesser of its operands,
  47      *         according to the supplied {@code Comparator}
  48      */
  49     public static<T> BinaryOperator<T> minBy(Comparator<? super T> comparator) {
  50         Objects.requireNonNull(comparator);
  51         return (a, b) -> comparator.compare(a, b) <= 0 ? a : b;
  52     }
  53 
  54     /**
  55      * Constructs a {@link BinaryOperator} which returns the greater of two elements
  56      * according to the specified {@code Comparator}
  57      *
  58      * @param  comparator A {@code Comparator} for comparing the two values
  59      * @return a {@code BinaryOperator} which returns the greater of its operands,
  60      *         according to the supplied {@code Comparator}
  61      */
  62     public static<T> BinaryOperator<T> maxBy(Comparator<? super T> comparator) {
  63         Objects.requireNonNull(comparator);
  64         return (a, b) -> comparator.compare(a, b) >= 0 ? a : b;
  65     }
  66 }
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