/*
 * 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);
}

/*
 * 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; a pre-Java-8 version of {@code
 * 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, reducing <i>explicit</i> dependencies on this type by using lambda expressions or
 * method references instead of classes will leave your code easier to migrate in the future.
 *
 * <p>If you need to use a reference of this type (say, named {@code guavaPredicate}) in a context
 * where {@code java.util.function.Predicate} is expected, use {@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
   */
  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);
}

Document Predicate vs. Java 8 issues. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=110185504