A list of useful regexp
[30 Oct 11 at 09:16:54 - 0 comment(s)]
regexp or in other words regular expression is something you have to regularly use in your applications. I've decided to write this post as a placeholder for regexp I believe are common and useful such as regexp for email validation or some you might use to replace characters in a string. I might write some piece of java code but you can use these regular expression in many other languages.
1. regexp for validating email address
^[\\w\\-]+(\\.[\\w\\-]+)*@([A-Za-z0-9-]+\\.)+[A-Za-z]{2,4}$
But here is actually what I use to validate email address:
public boolean isValidEmail(String input) {
Pattern p = Pattern.compile("^\\.|^\\@");
Matcher m = p.matcher(input);
if (m.find())
return false;
p = Pattern.compile("^www\\.");
m = p.matcher(input);
if (m.find())
return false;
p = Pattern.compile("[^A-Za-z0-9\\.\\@_\\-~#]+");
m = p.matcher(input);
StringBuffer sb = new StringBuffer();
boolean result = m.find();
boolean deletedIllegalChars = false;
while(result) {
deletedIllegalChars = true;
m.appendReplacement(sb, "");
result = m.find();
}
// Add the last segment of input to the new String
m.appendTail(sb);
input = sb.toString();
if(deletedIllegalChars)
return false;
return true;
}
Pattern p = Pattern.compile("^\\.|^\\@");
Matcher m = p.matcher(input);
if (m.find())
return false;
p = Pattern.compile("^www\\.");
m = p.matcher(input);
if (m.find())
return false;
p = Pattern.compile("[^A-Za-z0-9\\.\\@_\\-~#]+");
m = p.matcher(input);
StringBuffer sb = new StringBuffer();
boolean result = m.find();
boolean deletedIllegalChars = false;
while(result) {
deletedIllegalChars = true;
m.appendReplacement(sb, "");
result = m.find();
}
// Add the last segment of input to the new String
m.appendTail(sb);
input = sb.toString();
if(deletedIllegalChars)
return false;
return true;
}
2. regexp to validate username of type test@test
[^@/]+@[^@/]+
3. regexp to replace multiple spaces
\\s+
4. regexp to replace any characters that is not alphanumeric
[^a-zA-Z0-9]
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