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<TITLE>Applying Regular Expressions on the Contents of a File
(Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
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<B><A HREF="../java.util.regex/pkg.html">java.util.regex</A></B><font color="#666666" SIZE="-2">
[26 examples]
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<h3>
e425.
Applying Regular Expressions on the Contents of a File</h3>
The matching routines in <code>java.util.regex</code> require that the input be a
<code>CharSequence</code> object. This example implements a method that
efficiently returns the contents of a file in a <code>CharSequence</code> object.
<pre>
// Converts the contents of a file into a CharSequence
// suitable for use by the regex package.
public CharSequence fromFile(String filename) throws IOException {
FileInputStream fis = new FileInputStream(filename);
FileChannel fc = fis.getChannel();
// Create a read-only CharBuffer on the file
ByteBuffer bbuf = fc.map(FileChannel.MapMode.READ_ONLY, 0, (int)fc.size());
CharBuffer cbuf = Charset.forName("8859_1").newDecoder().decode(bbuf);
return cbuf;
}
</pre>
Here is sample code that uses the method:
<pre>
try {
// Create matcher on file
Pattern pattern = Pattern.compile(<font color="#0066ff"><i>"pattern"</i></font>);
Matcher matcher = pattern.matcher(fromFile(<font color="#0066ff"><i>"infile.txt"</i></font>));
// Find all matches
while (matcher.find()) {
// Get the matching string
String match = matcher.group();
}
} catch (IOException e) {
}
</pre>
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Related Examples
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e423. <a class="eglink" href="BasicMatch.html?l=rel">
Quintessential Regular Expression Search Program
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e424. <a class="eglink" href="MatchExactly.html?l=rel">
Determining If a String Matches a Pattern Exactly
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e426. <a class="eglink" href="RemDupSpace.html?l=rel">
Removing Duplicate Whitespace in a String
</a>
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e427. <a class="eglink" href="Greedy.html?l=rel">
Greedy and Nongreedy Matching in a Regular Expression
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e428. <a class="eglink" href="Escape.html?l=rel">
Escaping Special Characters in a Pattern
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See also:
<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Flags">
Flags
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<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Groups">
Groups
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<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Lines">
Lines
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<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Paragraphs">
Paragraphs
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<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Searching%20and%20Replacing">
Searching and Replacing
</a>
<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Tokenizing">
Tokenizing
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