1 /*
2 * Copyright (c) 2000, 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
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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 *
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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
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24 */
25
26 /**
27 * Defines buffers, which are containers for data, and provides an
28 * overview of the other NIO packages.
29 *
30 *
31 * <p> The central abstractions of the NIO APIs are: </p>
32 *
33 * <ul>
34 *
35 * <li><p> <a href="#buffers"><i>Buffers</i></a>, which are containers for data;
36 * </p></li>
37 *
38 * <li><p> <a
39 * href="charset/package-summary.html"><i>Charsets</i></a> and their
40 * associated <i>decoders</i> and <i>encoders</i>, <br> which
41 * translate between bytes and Unicode characters; </p></li>
42 *
43 * <li><p> <a
44 * href="channels/package-summary.html"><i>Channels</i></a> of
45 * various types, which represent connections <br> to entities
46 * capable of performing I/O operations; and </p></li>
47 *
48 * <li><p> <i>Selectors</i> and <i>selection keys</i>, which
49 * together with <br> <i>selectable channels</i> define a <a
50 * href="channels/package-summary.html#multiplex">multiplexed,
51 * non-blocking <br> I/O</a> facility. </p></li>
52 *
53 * </ul>
54 *
55 * <p> The {@code java.nio} package defines the buffer classes, which
56 * are used throughout the NIO APIs. The charset API is defined in
57 * the {@link java.nio.charset} package, and the channel and selector
58 * APIs are defined in the {@link java.nio.channels} package. Each of
59 * these subpackages has its own service-provider (SPI) subpackage,
60 * the contents of which can be used to extend the platform's default
61 * implementations or to construct alternative implementations.
62 *
63 * <a id="buffers"> </a>
64 *
65 * <blockquote><table cellspacing=1 cellpadding=0 summary="Description of the various buffers">
66 * <tr><th align="left">Buffers</th><th align="left">Description</th></tr>
67 * <tr><td valign=top>{@link java.nio.Buffer}</td>
68 * <td>Position, limit, and capacity;
69 * <br>clear, flip, rewind, and mark/reset</td></tr>
70 * <tr><td valign=top> {@link java.nio.ByteBuffer}</td>
71 * <td>Get/put, compact, views; allocate, wrap</td></tr>
72 * <tr><td valign=top> {@link java.nio.MappedByteBuffer} </td>
73 * <td>A byte buffer mapped to a file</td></tr>
74 * <tr><td valign=top> {@link java.nio.CharBuffer}</td>
75 * <td>Get/put, compact; allocate, wrap</td></tr>
76 * <tr><td valign=top> {@link java.nio.DoubleBuffer}</td>
77 * <td> ' '</td></tr>
78 * <tr><td valign=top> {@link java.nio.FloatBuffer}</td>
79 * <td> ' '</td></tr>
80 * <tr><td valign=top> {@link java.nio.IntBuffer}</td>
81 * <td> ' '</td></tr>
82 * <tr><td valign=top> {@link java.nio.LongBuffer}</td>
83 * <td> ' '</td></tr>
84 * <tr><td valign=top> {@link java.nio.ShortBuffer}</td>
85 * <td> ' '</td></tr>
86 * <tr><td valign=top>{@link java.nio.ByteOrder}</td>
87 * <td>Typesafe enumeration for byte orders</td></tr>
88 * </table></blockquote>
89 *
90 * <p> A <i>buffer</i> is a container for a fixed amount of data of a
91 * specific primitive type. In addition to its content a buffer has a
92 * <i>position</i>, which is the index of the next element to be read
93 * or written, and a <i>limit</i>, which is the index of the first
94 * element that should not be read or written. The base {@link
95 * java.nio.Buffer} class defines these properties as well as methods
96 * for <i>clearing</i>, <i>flipping</i>, and <i>rewinding</i>, for
97 * <i>marking</i> the current position, and for <i>resetting</i> the
98 * position to the previous mark.
99 *
100 * <p> There is a buffer class for each non-boolean primitive type.
101 * Each class defines a family of <i>get</i> and <i>put</i> methods
102 * for moving data out of and in to a buffer, methods for
103 * <i>compacting</i>, <i>duplicating</i>, and <i>slicing</i> a buffer,
104 * and static methods for <i>allocating</i> a new buffer as well as
105 * for <i>wrapping</i> an existing array into a buffer.
106 *
107 * <p> Byte buffers are distinguished in that they can be used as the
108 * sources and targets of I/O operations. They also support several
109 * features not found in the other buffer classes:
110 *
111 * <ul>
112 *
113 * <li><p> A byte buffer can be allocated as a <a
114 * href="ByteBuffer.html#direct"> <i>direct</i></a> buffer, in which
115 * case the Java virtual machine will make a best effort to perform
116 * native I/O operations directly upon it. </p></li>
117 *
118 * <li><p> A byte buffer can be created by {@link
119 * java.nio.channels.FileChannel#map <i>mapping</i>} a region of a
120 * file directly into memory, in which case a few additional
121 * file-related operations defined in the {@link
122 * java.nio.MappedByteBuffer} class are available. </p></li>
123 *
124 * <li><p> A byte buffer provides access to its content as either a
125 * heterogeneous or homogeneous sequence of <a
126 * href="ByteBuffer.html#bin"><i>binary data</i></a> of any
127 * non-boolean primitive type, in either big-endian or little-endian
128 * <a href="ByteOrder.html">byte order</a>. </p></li>
129 *
130 * </ul>
131 *
132 * <p> Unless otherwise noted, passing a {@code null} argument to a
133 * constructor or method in any class or interface in this package
134 * will cause a {@link java.lang.NullPointerException
135 * NullPointerException} to be thrown.
136 *
137 * @since 1.4
138 * @author Mark Reinhold
139 * @author JSR-51 Expert Group
140 */
141 package java.nio;