Is it a problem on Regex or Static

王朝other·作者佚名  2008-05-31
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I have met a problem, which will seriously cause JVM problem.

I try to build a class to solve String operation with Regular EXPression (Java.util.regex.*)

I define all the method as a static one, thus i can use the class to parse String without a instance. But when i use the method many times, just found the memory is quickly exhausted. ( i use java -verbose:gc to observe the status). finally , i focus on the return type of the method, i directly return the String with "m.group(1)" (m is a instance of java.util.regex.Matcher). Is it a problem of regex or static or both? i didn't know the answer.

The original code are:

public static String getFirstGroup(String regex, String original) {

Pattern p = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);

Matcher m = p.matcher(original);

if (m.find()) {

String result = m.group(1);

m = null;

return result;

} else {

return "";

}

}

The strange thing is when i use is to parse one same String for many times, on problem occurs.

Then i make some change:

public static String getFirstGroup(String regex, String original) {

Pattern p = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);

Matcher m = p.matcher(original);

if (m.find()) {

String result = new String(m.group(1));

m = null;

return result;

} else {

return "";

}

}

The problem disappeared. So i confused with the problem.

 
 
 
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