Is it a problem on Regex or Static

核心提示：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 defin

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.