creatememmap.html
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<TITLE>Creating a Memory-Mapped File
(Java Developers Almanac Example)
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<h3>
e166.
Creating a Memory-Mapped File</h3>
Mapping a file in memory results in a <code>ByteArray</code> object. To
access the byte array, see <a href="../java.nio/GetBytes.html" class="eglink"><font size="-1"><b>e159</b> Getting Bytes from a ByteBuffer</font></a> and
<a href="../java.nio/PutBytes.html" class="eglink"><font size="-1"><b>e160</b> Putting Bytes into a ByteBuffer</font></a>.
<pre>
try {
File file = new File(<font color="#0066ff"><i>"filename"</i></font>);
// Create a read-only memory-mapped file
FileChannel roChannel = new RandomAccessFile(file, "r").getChannel();
ByteBuffer roBuf = roChannel.map(FileChannel.MapMode.READ_ONLY, 0, (int)roChannel.size());
// Create a read-write memory-mapped file
FileChannel rwChannel = new RandomAccessFile(file, "rw").getChannel();
ByteBuffer wrBuf = rwChannel.map(FileChannel.MapMode.READ_WRITE, 0, (int)rwChannel.size());
// Create a private (copy-on-write) memory-mapped file.
// Any write to this channel results in a private copy of the data.
FileChannel pvChannel = new RandomAccessFile(file, "rw").getChannel();
ByteBuffer pvBuf = roChannel.map(FileChannel.MapMode.READ_WRITE, 0, (int)rwChannel.size());
} catch (IOException e) {
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Related Examples
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e167. <a class="eglink" href="Force.html?l=rel">
Persisting Changes to a Memory-Mapped ByteBuffer
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e168. <a class="eglink" href="IsDirect.html?l=rel">
Determining If a ByteBuffer Is Direct
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e169. <a class="eglink" href="ReadChannel.html?l=rel">
Reading from a Channel with a ByteBuffer
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e170. <a class="eglink" href="WriteChannel.html?l=rel">
Writing to a Channel with a ByteBuffer
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e171. <a class="eglink" href="WriteBuffer.html?l=rel">
Writing and Appending a ByteBuffer to a File
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e172. <a class="eglink" href="File2File.html?l=rel">
Copying One File to Another
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See also:
<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#Byte%20Buffers">
Byte Buffers
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<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#File%20Locking">
File Locking
</a>
<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#Sockets">
Sockets
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<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#Streams">
Streams
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