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 }