StringUtils.isBlank与Regexp

Question

So I am looking through some legacy code and finding instance where they do this:

if ((name == null) || (name.matches("\\s*")))
   .. do something

Ignore for the moment that the .matches(..) call creates a new Pattern and Matcher everytime (uhg) - but is there any reason not to change this line to:

if (StringUtils.isBlank(name))
   ..do something

I'm pretty sure the regex simply matches if the string is all whitespace. Will StringUtils catch all the same conditions as the first one?

Answer 1

Yes, StringUtils.isBlank(..) will do the same thing, and is a better way to go. Take a look at the code:

public static boolean isBlank(String str) {
     int strLen;
     if ((str == null) || ((strLen = str.length()) == 0))
         return true;
     int strLen;
     for (int i = 0; i < strLen; ++i) {
        if (!(Character.isWhitespace(str.charAt(i)))) {
           return false;
        }
     }
   return true;
}

Answer 2

You are correct the regular expression test's if the string is more zero or more white space characters.

The advantages of not using the regular expression

• Regular expressions are cryptic to many people, which makes it less readable
• And as you rightly pointed out .matches() has a non trivial overhead

Answer 3

 /**
 * Returns if the specified string is <code>null</code> or the empty string.
 * @param string the string
 * @return <code>true</code> if the specified string is <code>null</code> or the empty string, <code>false</code> otherwise
 */
public static boolean isEmptyOrNull(String string)
{
    return (null == string) || (0 >= string.length());
}