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25 package java.util.function;
26 
27 import java.util.Objects;
28 
29 /**
30  * Represents an operation on a single {@code long}-valued operand that produces
31  * a {@code long}-valued result.  This is the primitive type specialization of
32  * {@link UnaryOperator} for {@code long}.
33  *
34  * <p>This is a <a href="package-summary.html">functional interface</a>
35  * whose functional method is {@link #applyAsLong(long)}.
36  *
37  * @see UnaryOperator
38  * @since 1.8
39  */
40 @FunctionalInterface
41 public interface LongUnaryOperator {
42 
43     /**
44      * Applies this operator to the given operand.
45      *
46      * @param operand the operand
47      * @return the operator result
48      */
applyAsLong(long operand)49     long applyAsLong(long operand);
50 
51     /**
52      * Returns a composed operator that first applies the {@code before}
53      * operator to its input, and then applies this operator to the result.
54      * If evaluation of either operator throws an exception, it is relayed to
55      * the caller of the composed operator.
56      *
57      * @param before the operator to apply before this operator is applied
58      * @return a composed operator that first applies the {@code before}
59      * operator and then applies this operator
60      * @throws NullPointerException if before is null
61      *
62      * @see #andThen(LongUnaryOperator)
63      */
compose(LongUnaryOperator before)64     default LongUnaryOperator compose(LongUnaryOperator before) {
65         Objects.requireNonNull(before);
66         return (long v) -> applyAsLong(before.applyAsLong(v));
67     }
68 
69     /**
70      * Returns a composed operator that first applies this operator to
71      * its input, and then applies the {@code after} operator to the result.
72      * If evaluation of either operator throws an exception, it is relayed to
73      * the caller of the composed operator.
74      *
75      * @param after the operator to apply after this operator is applied
76      * @return a composed operator that first applies this operator and then
77      * applies the {@code after} operator
78      * @throws NullPointerException if after is null
79      *
80      * @see #compose(LongUnaryOperator)
81      */
andThen(LongUnaryOperator after)82     default LongUnaryOperator andThen(LongUnaryOperator after) {
83         Objects.requireNonNull(after);
84         return (long t) -> after.applyAsLong(applyAsLong(t));
85     }
86 
87     /**
88      * Returns a unary operator that always returns its input argument.
89      *
90      * @return a unary operator that always returns its input argument
91      */
identity()92     static LongUnaryOperator identity() {
93         return t -> t;
94     }
95 }
96