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13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
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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       */
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       */
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       */
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       */
92      static LongUnaryOperator identity() {
93          return t -> t;
94      }
95  }