The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2008 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.internal.util; |
| 18 | |
| 19 | import java.util.Arrays; |
| 20 | |
| 21 | /** |
| 22 | * Predicates contains static methods for creating the standard set of |
| 23 | * {@code Predicate} objects. |
| 24 | */ |
| 25 | public class Predicates { |
| 26 | |
| 27 | private Predicates() { |
| 28 | } |
| 29 | |
| 30 | /** |
| 31 | * Returns a Predicate that evaluates to true iff each of its components |
| 32 | * evaluates to true. The components are evaluated in order, and evaluation |
| 33 | * will be "short-circuited" as soon as the answer is determined. |
| 34 | */ |
| 35 | public static <T> Predicate<T> and(Predicate<? super T>... components) { |
| 36 | return and(Arrays.asList(components)); |
| 37 | } |
| 38 | |
| 39 | /** |
| 40 | * Returns a Predicate that evaluates to true iff each of its components |
| 41 | * evaluates to true. The components are evaluated in order, and evaluation |
| 42 | * will be "short-circuited" as soon as the answer is determined. Does not |
| 43 | * defensively copy the iterable passed in, so future changes to it will alter |
| 44 | * the behavior of this Predicate. If components is empty, the returned |
| 45 | * Predicate will always evaluate to true. |
| 46 | */ |
| 47 | public static <T> Predicate<T> and(Iterable<? extends Predicate<? super T>> components) { |
| 48 | return new AndPredicate(components); |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * Returns a Predicate that evaluates to true iff any one of its components |
| 53 | * evaluates to true. The components are evaluated in order, and evaluation |
| 54 | * will be "short-circuited" as soon as the answer is determined. |
| 55 | */ |
| 56 | public static <T> Predicate<T> or(Predicate<? super T>... components) { |
| 57 | return or(Arrays.asList(components)); |
| 58 | } |
| 59 | |
| 60 | /** |
| 61 | * Returns a Predicate that evaluates to true iff any one of its components |
| 62 | * evaluates to true. The components are evaluated in order, and evaluation |
| 63 | * will be "short-circuited" as soon as the answer is determined. Does not |
| 64 | * defensively copy the iterable passed in, so future changes to it will alter |
| 65 | * the behavior of this Predicate. If components is empty, the returned |
| 66 | * Predicate will always evaluate to false. |
| 67 | */ |
| 68 | public static <T> Predicate<T> or(Iterable<? extends Predicate<? super T>> components) { |
| 69 | return new OrPredicate(components); |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Returns a Predicate that evaluates to true iff the given Predicate |
| 74 | * evaluates to false. |
| 75 | */ |
| 76 | public static <T> Predicate<T> not(Predicate<? super T> predicate) { |
| 77 | return new NotPredicate<T>(predicate); |
| 78 | } |
| 79 | |
| 80 | private static class AndPredicate<T> implements Predicate<T> { |
| 81 | private final Iterable<? extends Predicate<? super T>> components; |
| 82 | |
| 83 | private AndPredicate(Iterable<? extends Predicate<? super T>> components) { |
| 84 | this.components = components; |
| 85 | } |
| 86 | |
| 87 | public boolean apply(T t) { |
| 88 | for (Predicate<? super T> predicate : components) { |
| 89 | if (!predicate.apply(t)) { |
| 90 | return false; |
| 91 | } |
| 92 | } |
| 93 | return true; |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | private static class OrPredicate<T> implements Predicate<T> { |
| 98 | private final Iterable<? extends Predicate<? super T>> components; |
| 99 | |
| 100 | private OrPredicate(Iterable<? extends Predicate<? super T>> components) { |
| 101 | this.components = components; |
| 102 | } |
| 103 | |
| 104 | public boolean apply(T t) { |
| 105 | for (Predicate<? super T> predicate : components) { |
| 106 | if (predicate.apply(t)) { |
| 107 | return true; |
| 108 | } |
| 109 | } |
| 110 | return false; |
| 111 | } |
| 112 | } |
| 113 | |
| 114 | private static class NotPredicate<T> implements Predicate<T> { |
| 115 | private final Predicate<? super T> predicate; |
| 116 | |
| 117 | private NotPredicate(Predicate<? super T> predicate) { |
| 118 | this.predicate = predicate; |
| 119 | } |
| 120 | |
| 121 | public boolean apply(T t) { |
| 122 | return !predicate.apply(t); |
| 123 | } |
| 124 | } |
| 125 | } |