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<TITLE>Using a Non-Capturing Group in a Regular Expression
(Java Developers Almanac Example)
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<h3>
e438.
Using a Non-Capturing Group in a Regular Expression</h3>
By default, a group captures text (see
<a href="../java.util.regex/Group.html" class="eglink"><font size="-1"><b>e436</b> Capturing Text in a Group in a Regular Expression</font></a>). In some cases, a group is needed
but there is no need to capture the text. A non-capturing group
should be used to improve performance. A non-capturing group starts
with <code>(?:</code>.
<pre>
String inputStr = <font color="#0066ff"><i>"abbabcd"</i></font>;
String patternStr = <font color="#0066ff"><i>"(a(?:b*))+(c*)"</i></font>;
// (?:b*) is a non-capturing group
// Compile and use regular expression
Pattern pattern = Pattern.compile(patternStr);
Matcher matcher = pattern.matcher(inputStr);
boolean matchFound = matcher.find();
if (matchFound) {
// Get all groups for this match
for (int i=0; i<=matcher.groupCount(); i++) {
String groupStr = matcher.group(i);
}
// group 0: abbabc
// group 1: ab
// group 2: c
}
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Related Examples
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e436. <a class="eglink" href="Group.html?l=rel">
Capturing Text in a Group in a Regular Expression
</a>
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e437. <a class="eglink" href="GroupIx.html?l=rel">
Getting the Indices of a Matching Group in a Regular Expression
</a>
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e439. <a class="eglink" href="GroupInPat.html?l=rel">
Using the Captured Text of a Group within a Pattern
</a>
<br>
e440. <a class="eglink" href="GroupInRep.html?l=rel">
Using the Captured Text of a Group within a Replacement Pattern
</a>
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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#Lines">
Lines
</a>
<a class="eglink" href="/egs/java.util.regex/pkg.html?l=rel#Paragraphs">
Paragraphs
</a>
<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
</a>
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