xref: /libcore/ojluni/src/main/java/java/util/stream/StreamShape.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package java.util.stream;

/**
 * An enum describing the known shape specializations for stream abstractions.
 * Each will correspond to a specific subinterface of {@link BaseStream}
 * (e.g., {@code REFERENCE} corresponds to {@code Stream}, {@code INT_VALUE}
 * corresponds to {@code IntStream}).  Each may also correspond to
 * specializations of value-handling abstractions such as {@code Spliterator},
 * {@code Consumer}, etc.
 *
 * @apiNote
 * This enum is used by implementations to determine compatibility between
 * streams and operations (i.e., if the output shape of a stream is compatible
 * with the input shape of the next operation).
 *
 * <p>Some APIs require you to specify both a generic type and a stream shape
 * for input or output elements, such as {@link TerminalOp} which has both
 * generic type parameters for its input types, and a getter for the
 * input shape.  When representing primitive streams in this way, the
 * generic type parameter should correspond to the wrapper type for that
 * primitive type.
 *
 * @since 1.8
 * @hide Visible for CTS testing only (OpenJDK8 tests).
 */
public enum StreamShape {
    /**
     * The shape specialization corresponding to {@code Stream} and elements
     * that are object references.
     */
    REFERENCE,
    /**
     * The shape specialization corresponding to {@code IntStream} and elements
     * that are {@code int} values.
     */
    INT_VALUE,
    /**
     * The shape specialization corresponding to {@code LongStream} and elements
     * that are {@code long} values.
     */
    LONG_VALUE,
    /**
     * The shape specialization corresponding to {@code DoubleStream} and
     * elements that are {@code double} values.
     */
    DOUBLE_VALUE
}