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