Problem with creating my own class...

Question

Hi all,
Purpose with this program:
I want to create my own class StringThing which take a string parameter and transform the content toUpperCase().
I have created a simple class StringThing which look like this:
class StringThing {
public String upperize (String u) {
u.toUpperCase();
return u;
}And my class where I use the StringThing looks like this:
import java.io.*;
class UseStringThing{
public static void main (String arg[]) throws Exception {
BufferedReader keyboard = new BufferedReader(
new InputStreamReader(System.in));
String s,p;
System.out.prinln("write a sentence!");
s=keyboard.readLine();
StringThing thing = new StringThing();
p=thing.upperize(s);
System.out.println(p);
}Am I not supposed to transform my string parameter in my class by using for instance toUpperCase()? Or is there some fundamental rule or piece of code which I forgot?
Thanks in advance,
/Beginner-T-who-ripps-his-hear-over-this-small-problem

Answer 1

Strings cannot be modified. What this line does:
u.toUpperCase();
is to create a new String object. toUpperCase() returns the newly created string and you are ignoring the returned value. What you want to do is:
return u.toUpperCase();
or
u = u.toUpperCase();