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 
  29 /**
  30  * Determines if the input object matches some criteria.
  31  *
  32  * @param <T> the type of argument to {@code test}
  33  *
  34  * @since 1.8
  35  */
  36 @FunctionalInterface
  37 public interface Predicate<T> {
  38 
  39     /**
  40      * Returns {@code true} if the input object matches some criteria.
  41      *
  42      * @param t the input object
  43      * @return {@code true} if the input object matches some criteria, otherwise
  44      * {@code false}
  45      */
  46     boolean test(T t);
  47 
  48     /**
  49      * Returns a predicate which evaluates to {@code true} only if this
  50      * predicate and the provided predicate both evaluate to {@code true}. If
  51      * this predicate returns {@code false} then the remaining predicate is not
  52      * evaluated.
  53      *
  54      * <p>Any exceptions thrown by either {@code test} method are relayed
  55      * to the caller; if performing first operation throws an exception, the
  56      * second operation will not be performed.
  57      *
  58      * @param p a predicate which will be logically-ANDed with this predicate
  59      * @return a new predicate which returns {@code true} only if both
  60      * predicates return {@code true}
  61      * @throws NullPointerException if p is null
  62      */
  63     default Predicate<T> and(Predicate<? super T> p) {
  64         Objects.requireNonNull(p);
  65         return (t) -> test(t) && p.test(t);
  66     }
  67 
  68     /**
  69      * Returns a predicate which negates the result of this predicate.
  70      *
  71      * @return a new predicate who's result is always the opposite of this
  72      * predicate.
  73      */
  74     default Predicate<T> negate() {
  75         return (t) -> !test(t);
  76     }
  77 
  78     /**
  79      * Returns a predicate which evaluates to {@code true} if either this
  80      * predicate or the provided predicate evaluates to {@code true}. If this
  81      * predicate returns {@code true} then the remaining predicate is not
  82      * evaluated.
  83      *
  84      * <p>Any exceptions thrown by either {@code test} method are relayed
  85      * to the caller; if performing first operation throws an exception, the
  86      * second operation will not be performed.
  87      *
  88      * @param p a predicate which will be logically-ORed with this predicate
  89      * @return a new predicate which returns {@code true} if either predicate
  90      * returns {@code true}
  91      * @throws NullPointerException if p is null
  92      */
  93     default Predicate<T> or(Predicate<? super T> p) {
  94         Objects.requireNonNull(p);
  95         return (t) -> test(t) || p.test(t);
  96     }
  97 
  98     /**
  99      * Returns a predicate who's result matches
 100      * {@code Objects.equals(target, t)}.
 101      *
 102      * @param <T> the type of values evaluated by the predicate
 103      * @param target the target value to be compared for equality
 104      * @return a predicate who's result matches
 105      * {@code Objects.equals(target, t)}
 106      */
 107     static <T> Predicate<T> isEqual(Object target) {
 108         return (null == target)
 109                 ? Objects::isNull
 110                 : object -> target.equals(object);
 111     }
 112 }