1 /*
   2  * Copyright (c) 2012, 2013, 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.Iterator;
  28 import java.util.Spliterator;
  29 
  30 /**
  31  * Base interface for stream types such as {@link Stream}, {@link IntStream},
  32  * etc.  Contains methods common to all stream types.
  33  *
  34  * @param <T> type of stream elements
  35  * @param <S> type of stream implementing {@code BaseStream}
  36  * @since 1.8
  37  */
  38 public interface BaseStream<T, S extends BaseStream<T, S>> {
  39     /**
  40      * Returns an iterator for the elements of this stream.
  41      *
  42      * <p>This is a <a href="package-summary.html#StreamOps">terminal
  43      * operation</a>.
  44      *
  45      * @return the element iterator for this stream
  46      */
  47     Iterator<T> iterator();
  48 
  49     /**
  50      * Returns a spliterator for the elements of this stream.
  51      *
  52      * <p>This is a <a href="package-summary.html#StreamOps">terminal
  53      * operation</a>.
  54      *
  55      * @return the element spliterator for this stream
  56      */
  57     Spliterator<T> spliterator();
  58 
  59     /**
  60      * Returns whether this stream, when executed, would execute in parallel
  61      * (assuming no further modification of the stream, such as appending
  62      * further intermediate operations or changing its parallelism).  Calling
  63      * this method after invoking an intermediate or terminal stream operation
  64      * method may yield unpredictable results.
  65      *
  66      * @return {@code true} if this stream would execute in parallel if executed
  67      * without further modification otherwise {@code false}
  68      */
  69     boolean isParallel();
  70 
  71     /**
  72      * Returns an equivalent stream that is sequential.  May return
  73      * itself, either because the stream was already sequential, or because
  74      * the underlying stream state was modified to be sequential.
  75      *
  76      * <p>This is an <a href="package-summary.html#StreamOps">intermediate
  77      * operation</a>.
  78      *
  79      * @return a sequential stream
  80      */
  81     S sequential();
  82 
  83     /**
  84      * Returns an equivalent stream that is parallel.  May return
  85      * itself, either because the stream was already parallel, or because
  86      * the underlying stream state was modified to be parallel.
  87      *
  88      * <p>This is an <a href="package-summary.html#StreamOps">intermediate
  89      * operation</a>.
  90      *
  91      * @return a parallel stream
  92      */
  93     S parallel();
  94 
  95     /**
  96      * Returns an equivalent stream that is
  97      * <a href="package-summary.html#Ordering">unordered</a>.  May return
  98      * itself if the stream was already unordered.
  99      *
 100      * <p>This is an <a href="package-summary.html#StreamOps">intermediate
 101      * operation</a>.
 102      *
 103      * @return an unordered stream
 104      */
 105     S unordered();
 106 }