1/*
2 * Copyright (C) 2007 Google Inc.
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
17package com.android.mail.lib.base;
18
19
20/**
21 * Determines a true or false value for a given input. For example, a
22 * {@code RegexPredicate} might implement {@code Predicate<String>}, and return
23 * {@code true} for any string that matches its given regular expression.
24 *
25 * <p>Implementations which may cause side effects upon evaluation are strongly
26 * encouraged to state this fact clearly in their API documentation.
27 *
28 * @author Kevin Bourrillion
29 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
30 */
31public interface Predicate<T> {
32
33  /*
34   * This interface does not extend Function<T, Boolean> because doing so would
35   * let predicates return null.
36   */
37
38  /**
39   * Applies this predicate to the given object.
40   *
41   * @param input the input that the predicate should act on
42   * @return the value of this predicate when applied to the input {@code t}
43   */
44  boolean apply(T input);
45
46  /**
47   * Indicates whether some other object is equal to this {@code Predicate}.
48   * This method can return {@code true} <i>only</i> if the specified object is
49   * also a {@code Predicate} and, for every input object {@code input}, it
50   * returns exactly the same value. Thus, {@code predicate1.equals(predicate2)}
51   * implies that either {@code predicate1.apply(input)} and
52   * {@code predicate2.apply(input)} are both {@code true} or both
53   * {@code false}.
54   *
55   * <p>Note that it is always safe <i>not</i> to override
56   * {@link Object#equals}.
57   */
58  boolean equals(Object obj);
59}
60