| Rahul Ravikumar | 0533600 | 2019-10-14 15:04:32 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2000, 2004, 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 | |
| 26 | /** |
| 27 | * Defines buffers, which are containers for data, and provides an overview of the |
| 28 | * 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 href="charset/package-summary.html"><i>Charsets</i></a> and their |
| 39 | * associated <i>decoders</i> and <i>encoders</i>, <br> which translate between |
| 40 | * bytes and Unicode characters; </p></li> |
| 41 | * |
| 42 | * <li><p> <a href="channels/package-summary.html"><i>Channels</i></a> of |
| 43 | * various types, which represent connections <br> to entities capable of |
| 44 | * performing I/O operations; and </p></li> |
| 45 | * |
| 46 | * <li><p> <i>Selectors</i> and <i>selection keys</i>, which together with <br> |
| 47 | * <i>selectable channels</i> define a <a |
| 48 | * href="channels/package-summary.html#multiplex">multiplexed, non-blocking <br> |
| 49 | * I/O</a> facility. </p></li> |
| 50 | * |
| 51 | * </ul> |
| 52 | * |
| 53 | * <p> The <tt>java.nio</tt> package defines the buffer classes, which are used |
| 54 | * throughout the NIO APIs. The charset API is defined in the {@link |
| 55 | * java.nio.charset} package, and the channel and selector APIs are defined in the |
| 56 | * {@link java.nio.channels} package. Each of these subpackages has its own |
| 57 | * service-provider (SPI) subpackage, the contents of which can be used to extend |
| 58 | * the platform's default implementations or to construct alternative |
| 59 | * implementations. |
| 60 | * |
| 61 | * |
| 62 | * <a name="buffers"> |
| 63 | * |
| 64 | * <blockquote><table cellspacing=1 cellpadding=0 summary="Description of the various buffers"> |
| 65 | * <tr><th><p align="left">Buffers</p></th><th><p align="left">Description</p></th></tr> |
| 66 | * <tr><td valign=top><tt>{@link java.nio.Buffer}</tt></td> |
| 67 | * <td>Position, limit, and capacity; |
| 68 | * <br>clear, flip, rewind, and mark/reset</td></tr> |
| 69 | * <tr><td valign=top><tt> {@link java.nio.ByteBuffer}</tt></td> |
| 70 | * <td>Get/put, compact, views; allocate, wrap</td></tr> |
| 71 | * <tr><td valign=top><tt> {@link java.nio.MappedByteBuffer} </tt></td> |
| 72 | * <td>A byte buffer mapped to a file</td></tr> |
| 73 | * <tr><td valign=top><tt> {@link java.nio.CharBuffer}</tt></td> |
| 74 | * <td>Get/put, compact; allocate, wrap</td></tr> |
| 75 | * <tr><td valign=top><tt> {@link java.nio.DoubleBuffer}</tt></td> |
| 76 | * <td> ' '</td></tr> |
| 77 | * <tr><td valign=top><tt> {@link java.nio.FloatBuffer}</tt></td> |
| 78 | * <td> ' '</td></tr> |
| 79 | * <tr><td valign=top><tt> {@link java.nio.IntBuffer}</tt></td> |
| 80 | * <td> ' '</td></tr> |
| 81 | * <tr><td valign=top><tt> {@link java.nio.LongBuffer}</tt></td> |
| 82 | * <td> ' '</td></tr> |
| 83 | * <tr><td valign=top><tt> {@link java.nio.ShortBuffer}</tt></td> |
| 84 | * <td> ' '</td></tr> |
| 85 | * <tr><td valign=top><tt>{@link java.nio.ByteOrder}</tt></td> |
| 86 | * <td>Typesafe enumeration for byte orders</td></tr> |
| 87 | * </table></blockquote> |
| 88 | * |
| 89 | * <p> A <i>buffer</i> is a container for a fixed amount of data of a specific |
| 90 | * primitive type. In addition to its content a buffer has a <i>position</i>, |
| 91 | * which is the index of the next element to be read or written, and a |
| 92 | * <i>limit</i>, which is the index of the first element that should not be read |
| 93 | * or written. The base {@link java.nio.Buffer} class defines these properties as |
| 94 | * well as methods for <i>clearing</i>, <i>flipping</i>, and <i>rewinding</i>, for |
| 95 | * <i>marking</i> the current position, and for <i>resetting</i> the position to |
| 96 | * the previous mark. |
| 97 | * |
| 98 | * <p> There is a buffer class for each non-boolean primitive type. Each class |
| 99 | * defines a family of <i>get</i> and <i>put</i> methods for moving data out of |
| 100 | * and in to a buffer, methods for <i>compacting</i>, <i>duplicating</i>, and |
| 101 | * <i>slicing</i> a buffer, and static methods for <i>allocating</i> a new buffer |
| 102 | * as well as for <i>wrapping</i> an existing array into a buffer. |
| 103 | * |
| 104 | * <p> Byte buffers are distinguished in that they can be used as the sources and |
| 105 | * targets of I/O operations. They also support several features not found in the |
| 106 | * other buffer classes: |
| 107 | * |
| 108 | * <ul> |
| 109 | * |
| 110 | * <li><p> A byte buffer can be allocated as a <a href="ByteBuffer.html#direct"> |
| 111 | * <i>direct</i></a> buffer, in which case the Java virtual machine will make a |
| 112 | * best effort to perform native I/O operations directly upon it. </p></li> |
| 113 | * |
| 114 | * <li><p> A byte buffer can be created by {@link |
| 115 | * java.nio.channels.FileChannel#map </code><i>mapping</i><code>} a region of a |
| 116 | * file directly into memory, in which case a few additional file-related |
| 117 | * operations defined in the {@link java.nio.MappedByteBuffer} class are |
| 118 | * available. </p></li> |
| 119 | * |
| 120 | * <li><p> A byte buffer provides access to its content as either a heterogeneous |
| 121 | * or homogeneous sequence of <a href="ByteBuffer.html#bin">binary data</i></a> |
| 122 | * of any non-boolean primitive type, in either big-endian or little-endian <a |
| 123 | * href="ByteOrder.html">byte order</a>. </p></li> |
| 124 | * |
| 125 | * </ul> |
| 126 | * |
| 127 | * <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor |
| 128 | * or method in any class or interface in this package will cause a {@link |
| 129 | * java.lang.NullPointerException NullPointerException} to be thrown. |
| 130 | * |
| 131 | * @since 1.4 |
| 132 | * @author Mark Reinhold |
| 133 | * @author JSR-51 Expert Group |
| 134 | */ |
| 135 | |
| 136 | package java.nio; |
