You need to strip or trim a string of extraneous whitespace, control characters, or other specified characters.
StringUtils.trim()
takes a string and removes every whitespace
and control character from the beginning and the end:
String test1 = " a Testing 1 2 3 "; String test2 = " "; String trimTest1 = StringUtils.trim( test1 ); String trimTest2 = StringUtils.trimToNull( test2 ); System.out.println( trimTest1 ); System.our.println( trimTest2 );
This code produces the following result. The test1
variable is trimmed of leading and trailing whitespace, and the
test2 variable is trimmed to
null:
Testing 1 2 3 null
A control character
is defined as all characters below 32 on the ASCII
table—everything from 0
(NUL) to 31
(unit
separator).
StringUtils.trim( ) delegates to the
trim( ) function on String and
gracefully handles null. When you pass a
null to StringUtils.trim( ), it
returns a null.
If a string contains leading and trailing characters to be removed,
you can remove them with StringUtils.strip( ). The
strip( ) method differs from trim( ) in that you can specify a set of characters to strip from
the beginning and end of a string. In this example, dashes and
asterisks are stripped from the start and end of a string:
String original = "-------***---SHAZAM!---***-------"; String stripped = StringUtils.strip( original, "-*" ); System.out.println( "Stripped: " + stripped )
This produces the following output:
Stripped: SHAZAM!
Use trimToNull( )
to test if a given parameter is present.
Take the following servlet code as an example:
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
String companyName =
StringUtils.trimToNull( request.getParameter("companyName") );
if( companyName != null ) {
response.getWriter( ).write( "You supplied a company name!" );
}
}Using StringUtils reduces code complexity
incrementally—four or five lines of code at a time. Testing for
the absence or emptiness of a string usually entails checking to see
if a string is empty or of zero length, and because a string could be
null, you always need to check for
null to avoid throwing a
NullPointerException. In this last example, empty
has the same meaning as null—the
StringUtils.trimToNull( ) method takes a string as
a parameter, and if it is null or empty, the
method returns a null.