1 package java.util.function;
2
3 import java.util.Objects;
4
5 /**
6 * Represents a predicate (boolean-valued function) of one argument.
7 *
8 * <p>This is a <a href="package-summary.html">functional interface</a>
9 * whose functional method is {@link #test(Object)}.
10 *
11 * @param <T> the type of the input to the predicate
12 *
13 * @since 1.8
14 */
15 @FunctionalInterface
16 public interface Predicate<T> {
17
18 /**
19 * Evaluates this predicate on the given argument.
20 *
21 * @param t the input argument
22 * @return {@code true} if the input argument matches the predicate,
23 * otherwise {@code false}
24 */
25 boolean test(T t);
26
27 /**
28 * Returns a composed predicate that represents a short-circuiting logical
29 * AND of this predicate and another. When evaluating the composed
30 * predicate, if this predicate is {@code false}, then the {@code other}
31 * predicate is not evaluated.
32 *
33 * <p>Any exceptions thrown during evaluation of either predicate are relayed
34 * to the caller; if evaluation of this predicate throws an exception, the
35 * {@code other} predicate will not be evaluated.
36 *
37 * @param other a predicate that will be logically-ANDed with this
38 * predicate
39 * @return a composed predicate that represents the short-circuiting logical
40 * AND of this predicate and the {@code other} predicate
41 * @throws NullPointerException if other is null
42 */
43 default Predicate<T> and(Predicate<? super T> other) {
44 Objects.requireNonNull(other);
45 return (t) -> test(t) && other.test(t);
46 }
47
48 /**
49 * Returns a predicate that represents the logical negation of this
50 * predicate.
51 *
52 * @return a predicate that represents the logical negation of this
53 * predicate
54 */
55 default Predicate<T> negate() {
56 return (t) -> !test(t);
57 }
58
59 /**
60 * Returns a composed predicate that represents a short-circuiting logical
61 * OR of this predicate and another. When evaluating the composed
62 * predicate, if this predicate is {@code true}, then the {@code other}
63 * predicate is not evaluated.
64 *
65 * <p>Any exceptions thrown during evaluation of either predicate are relayed
66 * to the caller; if evaluation of this predicate throws an exception, the
67 * {@code other} predicate will not be evaluated.
68 *
69 * @param other a predicate that will be logically-ORed with this
70 * predicate
71 * @return a composed predicate that represents the short-circuiting logical
72 * OR of this predicate and the {@code other} predicate
73 * @throws NullPointerException if other is null
74 */
75 default Predicate<T> or(Predicate<? super T> other) {
76 Objects.requireNonNull(other);
77 return (t) -> test(t) || other.test(t);
78 }
79
80 /**
81 * Returns a predicate that tests if two arguments are equal according
82 * to {@link Objects#equals(Object, Object)}.
83 *
84 * @param <T> the type of arguments to the predicate
85 * @param targetRef the object reference with which to compare for equality,
86 * which may be {@code null}
87 * @return a predicate that tests if two arguments are equal according
88 * to {@link Objects#equals(Object, Object)}
89 */
90 static <T> Predicate<T> isEqual(Object targetRef) {
91 return (null == targetRef)
92 ? Objects::isNull
93 : object -> targetRef.equals(object);
94 }
95 }
