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/*
 * 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}.
 *
 * 

The {@link Predicates} class provides common predicates and related utilities. * *

See the Guava User Guide article on the use of {@code Predicate}. * *

For Java 8+ users

* *

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 explicit dependencies on this type by using lambda expressions * or method references instead of classes, leaving your code easier to migrate in the future. * *

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 extend {@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 { /** * Returns the result of applying this predicate to {@code input} (Java 8 users, see notes in the * class documentation above). This method is generally expected, but not absolutely * required, to have the following properties: * *

    *
  • Its execution does not cause any observable side effects. *
  • The computation is consistent with equals; that is, {@link Objects#equal * Objects.equal}{@code (a, b)} implies that {@code predicate.apply(a) == * predicate.apply(b))}. *
* * @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. * *

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 interchangeable with this one. "Interchangeable" * typically 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 not to be interchangeable. */ @Override boolean equals(@NullableDecl Object object); }





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