1 /*
   2  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  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
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.util.stream;
  26 
  27 import java.util.function.ToIntFunction;
  28 
  29 /**
  30  * An enum describing the known shape specializations for stream abstractions.  Each will correspond to
  31  * a specific subinterface of {@link BaseStream} (e.g., {@code REFERENCE} corresponds to {@code Stream},
  32  * {@code INT_VALUE} corresponds to {@code IntStream}).  Each may also correspond to specializations of
  33  * value-handling abstractions such as {@code Spliterator}, {@code Consumer}, etc.
  34  *
  35  * @apiNote
  36  * This enum is used by implementations to determine compatibility between streams and operations (i.e., if the
  37  * output shape of a stream is compatible with the input shape of the next operation).  It is also used to reduce
  38  * the code bloat associated with having multiple specialized stream types for primitives by allowing some code
  39  * to be largely shape-independent.
  40  *
  41  * <p>Some APIs require you to specify both a generic type and a stream shape for input or output elements, such as
  42  * {@link IntermediateOp} which has both generic type parameters for its input and output types, and getters for
  43  * the input and output shape.  When representing primitive streams in this way, the generic type parameter should
  44  * correspond to the wrapper type for that primitive type.  Accordingly, the {@code IntermediateOp} implementating
  45  * {@link Stream#map(ToIntFunction)} would have an output type parameter of {@code Integer} and an output
  46  * shape of @{code INT_VALUE}.
  47  * @since 1.8
  48  */
  49 enum StreamShape {
  50     REFERENCE,
  51     INT_VALUE,
  52     LONG_VALUE,
  53     DOUBLE_VALUE
  54 }