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25 package java.util.stream;
26 
27 /**
28  * An enum describing the known shape specializations for stream abstractions.
29  * Each will correspond to a specific subinterface of {@link BaseStream}
30  * (e.g., {@code REFERENCE} corresponds to {@code Stream}, {@code INT_VALUE}
31  * corresponds to {@code IntStream}).  Each may also correspond to
32  * specializations of value-handling abstractions such as {@code Spliterator},
33  * {@code Consumer}, etc.
34  *
35  * @apiNote
36  * This enum is used by implementations to determine compatibility between
37  * streams and operations (i.e., if the output shape of a stream is compatible
38  * with the input shape of the next operation).
39  *
40  * <p>Some APIs require you to specify both a generic type and a stream shape
41  * for input or output elements, such as {@link TerminalOp} which has both
42  * generic type parameters for its input types, and a getter for the
43  * input shape.  When representing primitive streams in this way, the
44  * generic type parameter should correspond to the wrapper type for that
45  * primitive type.
46  *
47  * @since 1.8
48  * @hide Visible for CTS testing only (OpenJDK8 tests).
49  */
50 public enum StreamShape {
51     /**
52      * The shape specialization corresponding to {@code Stream} and elements
53      * that are object references.
54      */
55     REFERENCE,
56     /**
57      * The shape specialization corresponding to {@code IntStream} and elements
58      * that are {@code int} values.
59      */
60     INT_VALUE,
61     /**
62      * The shape specialization corresponding to {@code LongStream} and elements
63      * that are {@code long} values.
64      */
65     LONG_VALUE,
66     /**
67      * The shape specialization corresponding to {@code DoubleStream} and
68      * elements that are {@code double} values.
69      */
70     DOUBLE_VALUE
71 }
72