| /* |
| * Copyright (C) 2007 The Guava Authors |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except |
| * in compliance with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software distributed under the License |
| * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express |
| * or implied. See the License for the specific language governing permissions and limitations under |
| * the License. |
| */ |
| |
| package com.google.common.base; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** |
| * Determines a true or false value for a given input; a pre-Java-8 version of {@link |
| * java.util.function.Predicate java.util.function.Predicate}. |
| * |
| * <p>The {@link Predicates} class provides common predicates and related utilities. |
| * |
| * <p>See the Guava User Guide article on <a |
| * href="https://github.com/google/guava/wiki/FunctionalExplained">the use of {@code Predicate}</a>. |
| * |
| * <h3>For Java 8+ users</h3> |
| * |
| * <p>This interface is now a legacy type. Use {@code java.util.function.Predicate} (or the |
| * appropriate primitive specialization such as {@code IntPredicate}) instead whenever possible. |
| * Otherwise, at least reduce <i>explicit</i> dependencies on this type by using lambda expressions |
| * or method references instead of classes, leaving your code easier to migrate in the future. |
| * |
| * <p>To use a reference of this type (say, named {@code guavaPredicate}) in a context where {@code |
| * java.util.function.Predicate} is expected, use the method reference {@code |
| * guavaPredicate::apply}. For the other direction, use {@code javaUtilPredicate::test}. A future |
| * version of this interface will be made to <i>extend</i> {@code java.util.function.Predicate}, so |
| * that conversion will be necessary in only one direction. At that time, this interface will be |
| * officially discouraged. |
| * |
| * @author Kevin Bourrillion |
| * @since 2.0 |
| */ |
| @GwtCompatible |
| public interface Predicate<T> { |
| /** |
| * Returns the result of applying this predicate to {@code input} (Java 8 users, see notes in the |
| * class documentation above). This method is <i>generally expected</i>, but not absolutely |
| * required, to have the following properties: |
| * |
| * <ul> |
| * <li>Its execution does not cause any observable side effects. |
| * <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal |
| * Objects.equal}{@code (a, b)} implies that {@code predicate.apply(a) == |
| * predicate.apply(b))}. |
| * </ul> |
| * |
| * @throws NullPointerException if {@code input} is null and this predicate does not accept null |
| * arguments |
| */ |
| @CanIgnoreReturnValue |
| boolean apply(@NullableDecl T input); |
| |
| /** |
| * Indicates whether another object is equal to this predicate. |
| * |
| * <p>Most implementations will have no reason to override the behavior of {@link Object#equals}. |
| * However, an implementation may also choose to return {@code true} whenever {@code object} is a |
| * {@link Predicate} that it considers <i>interchangeable</i> with this one. "Interchangeable" |
| * <i>typically</i> means that {@code this.apply(t) == that.apply(t)} for all {@code t} of type |
| * {@code T}). Note that a {@code false} result from this method does not imply that the |
| * predicates are known <i>not</i> to be interchangeable. |
| */ |
| @Override |
| boolean equals(@NullableDecl Object object); |
| } |