com.google.common.base.Predicate.java Source code

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Here is the source code for com.google.common.base.Predicate.java

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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 javax.annotation.Nullable;

/**
 * Determines a true or false value for a given input.
 *
 * <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>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
public interface Predicate<T> {
    /**
     * Returns the result of applying this predicate to {@code input}. 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
     */
    boolean apply(@Nullable 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(@Nullable Object object);
}