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<!--
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Copyright (c) 2000, 2004, Oracle and/or its affiliates. All rights reserved.
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DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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This code is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License version 2 only, as
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published by the Free Software Foundation. Oracle designates this
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particular file as subject to the "Classpath" exception as provided
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by Oracle in the LICENSE file that accompanied this code.
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This code is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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version 2 for more details (a copy is included in the LICENSE file that
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accompanied this code).
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You should have received a copy of the GNU General Public License version
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2 along with this work; if not, write to the Free Software Foundation,
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Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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or visit www.oracle.com if you need additional information or have any
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questions.
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-->
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<!doctype html public "-//IETF//DTD HTML//EN">
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<html>
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<body bgcolor="white">
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Defines buffers, which are containers for data, and provides an overview of the
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other NIO packages.
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<p> The central abstractions of the NIO APIs are: </p>
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<ul>
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<li><p> <a href="#buffers"><i>Buffers</i></a>, which are containers for data;
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</p></li>
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<li><p> <a href="charset/package-summary.html"><i>Charsets</i></a> and their
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associated <i>decoders</i> and <i>encoders</i>, <br> which translate between
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bytes and Unicode characters; </p></li>
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<li><p> <a href="channels/package-summary.html"><i>Channels</i></a> of
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various types, which represent connections <br> to entities capable of
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performing I/O operations; and </p></li>
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<li><p> <i>Selectors</i> and <i>selection keys</i>, which together with <br>
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<i>selectable channels</i> define a <a
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href="channels/package-summary.html#multiplex">multiplexed, non-blocking <br>
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I/O</a> facility. </p></li>
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</ul>
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<p> The <tt>java.nio</tt> package defines the buffer classes, which are used
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throughout the NIO APIs. The charset API is defined in the {@link
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java.nio.charset} package, and the channel and selector APIs are defined in the
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{@link java.nio.channels} package. Each of these subpackages has its own
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service-provider (SPI) subpackage, the contents of which can be used to extend
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the platform's default implementations or to construct alternative
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implementations.
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<a name="buffers">
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<blockquote><table cellspacing=1 cellpadding=0 summary="Description of the various buffers">
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<tr><th><p align="left">Buffers</p></th><th><p align="left">Description</p></th></tr>
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<tr><td valign=top><tt>{@link java.nio.Buffer}</tt></td>
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<td>Position, limit, and capacity;
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<br>clear, flip, rewind, and mark/reset</td></tr>
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<tr><td valign=top><tt> {@link java.nio.ByteBuffer}</tt></td>
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<td>Get/put, compact, views; allocate, wrap</td></tr>
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<tr><td valign=top><tt> {@link java.nio.MappedByteBuffer} </tt></td>
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<td>A byte buffer mapped to a file</td></tr>
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<tr><td valign=top><tt> {@link java.nio.CharBuffer}</tt></td>
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<td>Get/put, compact; allocate, wrap</td></tr>
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<tr><td valign=top><tt> {@link java.nio.DoubleBuffer}</tt></td>
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<td> ' '</td></tr>
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<tr><td valign=top><tt> {@link java.nio.FloatBuffer}</tt></td>
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<td> ' '</td></tr>
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<tr><td valign=top><tt> {@link java.nio.IntBuffer}</tt></td>
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<td> ' '</td></tr>
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<tr><td valign=top><tt> {@link java.nio.LongBuffer}</tt></td>
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<td> ' '</td></tr>
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<tr><td valign=top><tt> {@link java.nio.ShortBuffer}</tt></td>
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<td> ' '</td></tr>
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<tr><td valign=top><tt>{@link java.nio.ByteOrder}</tt></td>
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<td>Typesafe enumeration for byte orders</td></tr>
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</table></blockquote>
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<p> A <i>buffer</i> is a container for a fixed amount of data of a specific
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primitive type. In addition to its content a buffer has a <i>position</i>,
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which is the index of the next element to be read or written, and a
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<i>limit</i>, which is the index of the first element that should not be read
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or written. The base {@link java.nio.Buffer} class defines these properties as
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well as methods for <i>clearing</i>, <i>flipping</i>, and <i>rewinding</i>, for
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<i>marking</i> the current position, and for <i>resetting</i> the position to
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the previous mark.
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<p> There is a buffer class for each non-boolean primitive type. Each class
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defines a family of <i>get</i> and <i>put</i> methods for moving data out of
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and in to a buffer, methods for <i>compacting</i>, <i>duplicating</i>, and
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<i>slicing</i> a buffer, and static methods for <i>allocating</i> a new buffer
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as well as for <i>wrapping</i> an existing array into a buffer.
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<p> Byte buffers are distinguished in that they can be used as the sources and
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targets of I/O operations. They also support several features not found in the
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other buffer classes:
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<ul>
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<li><p> A byte buffer can be allocated as a <a href="ByteBuffer.html#direct">
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<i>direct</i></a> buffer, in which case the Java virtual machine will make a
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best effort to perform native I/O operations directly upon it. </p></li>
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<li><p> A byte buffer can be created by {@link
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java.nio.channels.FileChannel#map </code><i>mapping</i><code>} a region of a
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file directly into memory, in which case a few additional file-related
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operations defined in the {@link java.nio.MappedByteBuffer} class are
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available. </p></li>
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<li><p> A byte buffer provides access to its content as either a heterogeneous
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or homogeneous sequence of <a href="ByteBuffer.html#bin">binary data</i></a>
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of any non-boolean primitive type, in either big-endian or little-endian <a
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href="ByteOrder.html">byte order</a>. </p></li>
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</ul>
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<p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
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or method in any class or interface in this package will cause a {@link
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java.lang.NullPointerException NullPointerException} to be thrown.
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@since 1.4
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@author Mark Reinhold
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@author JSR-51 Expert Group
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</body>
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</html>
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