Predicate.java revision d052fb54474c6e3d99da861b02e4b49ac98790cc
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 */ 25package java.util.function; 26 27import java.util.Objects; 28 29/** 30 * Represents a predicate (boolean-valued function) of one argument. 31 * 32 * <p>This is a <a href="package-summary.html">functional interface</a> 33 * whose functional method is {@link #test(Object)}. 34 * 35 * @param <T> the type of the input to the predicate 36 * 37 * @since 1.8 38 * @hide 1.8 39 */ 40@FunctionalInterface 41public interface Predicate<T> { 42 43 /** 44 * Evaluates this predicate on the given argument. 45 * 46 * @param t the input argument 47 * @return {@code true} if the input argument matches the predicate, 48 * otherwise {@code false} 49 */ 50 boolean test(T t); 51 52 /** 53 * Returns a composed predicate that represents a short-circuiting logical 54 * AND of this predicate and another. When evaluating the composed 55 * predicate, if this predicate is {@code false}, then the {@code other} 56 * predicate is not evaluated. 57 * 58 * <p>Any exceptions thrown during evaluation of either predicate are relayed 59 * to the caller; if evaluation of this predicate throws an exception, the 60 * {@code other} predicate will not be evaluated. 61 * 62 * @param other a predicate that will be logically-ANDed with this 63 * predicate 64 * @return a composed predicate that represents the short-circuiting logical 65 * AND of this predicate and the {@code other} predicate 66 * @throws NullPointerException if other is null 67 */ 68 default Predicate<T> and(Predicate<? super T> other) { 69 Objects.requireNonNull(other); 70 return (t) -> test(t) && other.test(t); 71 } 72 73 /** 74 * Returns a predicate that represents the logical negation of this 75 * predicate. 76 * 77 * @return a predicate that represents the logical negation of this 78 * predicate 79 */ 80 default Predicate<T> negate() { 81 return (t) -> !test(t); 82 } 83 84 /** 85 * Returns a composed predicate that represents a short-circuiting logical 86 * OR of this predicate and another. When evaluating the composed 87 * predicate, if this predicate is {@code true}, then the {@code other} 88 * predicate is not evaluated. 89 * 90 * <p>Any exceptions thrown during evaluation of either predicate are relayed 91 * to the caller; if evaluation of this predicate throws an exception, the 92 * {@code other} predicate will not be evaluated. 93 * 94 * @param other a predicate that will be logically-ORed with this 95 * predicate 96 * @return a composed predicate that represents the short-circuiting logical 97 * OR of this predicate and the {@code other} predicate 98 * @throws NullPointerException if other is null 99 */ 100 default Predicate<T> or(Predicate<? super T> other) { 101 Objects.requireNonNull(other); 102 return (t) -> test(t) || other.test(t); 103 } 104 105 /** 106 * Returns a predicate that tests if two arguments are equal according 107 * to {@link Objects#equals(Object, Object)}. 108 * 109 * @param <T> the type of arguments to the predicate 110 * @param targetRef the object reference with which to compare for equality, 111 * which may be {@code null} 112 * @return a predicate that tests if two arguments are equal according 113 * to {@link Objects#equals(Object, Object)} 114 */ 115 static <T> Predicate<T> isEqual(Object targetRef) { 116 return (null == targetRef) 117 ? Objects::isNull 118 : object -> targetRef.equals(object); 119 } 120} 121