value is lost from a return statement! what??

ludeKing · 05-30-2004, 07:57 AM

Hi all, having a major problem with this code.
Basically I am asking a value to be returned from a method, but it is lost!

When the addNewUser() method is called, it then calls a bunch of different methods ot get values etc and then they will be collated into a profile/user account of that user.
The actual capture of the user input works, but it is lost on return! how come?

my class

Code:

import java.io.*;

class userUtility {

static String username;

public static void addNewUser() {  

newUserUsername(); //get the username from the other method
(other calls to methods to go in here later)
System.out.println(username);    //THIS PRINTS NULL. argh.

}

public static String newUserUsername() {
System.out.println(" \n\t\t+==============================+");
System.out.println("\t\t| SLMS: Register as a new user |");
System.out.println(" \t\t+==============================+\n");

    try{
	BufferedReader user = new BufferedReader(new InputStreamReader(System.in));
	System.out.println("\t\t Login name for new user or 'quit' to return to the main menu:\n");
	String username = user.readLine(); //get the input

	username = username.trim(); //get rid of any leading-trailing whitespace
	System.out.println(username);    //THIS WORKS FINE!

    }
    catch(IOException ioe){
    System.out.println("Invalid username! Please try again!");
    newUserUsername(); //reload the method.
    }
return username;    //BUT AFTER THIS THE VALUE IS LOST!
}
}

Any pointers would be appreciated because I have a different class which does pretty much the same this and the code is exactly the same (except the other class has the 'main' method).

Hko · 05-30-2004, 08:18 AM

Remove the red word.

Code:

import java.io.*;

class userUtility {

static String username;

public static void addNewUser() {  

newUserUsername(); //get the username from the other method
(other calls to methods to go in here later)
System.out.println(username);    //THIS PRINTS NULL. argh.

}

public static String newUserUsername() {
System.out.println(" \n\t\t+==============================+");
System.out.println("\t\t| SLMS: Register as a new user |");
System.out.println(" \t\t+==============================+\n");

    try{
	BufferedReader user = new BufferedReader(new InputStreamReader(System.in));
	System.out.println("\t\t Login name for new user or 'quit' to return to the main menu:\n");
	String username = user.readLine(); //get the input

	username = username.trim(); //get rid of any leading-trailing whitespace
	System.out.println(username);    //THIS WORKS FINE!

    }
    catch(IOException ioe){
    System.out.println("Invalid username! Please try again!");
    newUserUsername(); //reload the method.
    }
return username;    //BUT AFTER THIS THE VALUE IS LOST!
}
}

By having "String" in "String username = user.readLine()" you are creating another string-object named "username". This different string is only valid within "try {" ... "}". After that is gone, and if you then refer to username again, the global one will be referred to, which is not assgned a value yet.

So by remove "String" from the line "String username = user.readLine()" the identifier "username" inside the "try {" ... "}" will also refer to the global one, because now there is no other object named "username".

eric.r.turner · 05-30-2004, 01:21 PM

Quote:

Originally posted by Hko
Remove the red word.

Code:

String username = user.readLine(); //get the input

Alternatively you could leave the String in, and instead capture the return value of newUsername:

Code:

public static void addNewUser() {  
   username = newUserUsername(); //get the username from the other method
   (other calls to methods to go in here later)
   System.out.println(username);    //THIS PRINTS NULL. argh.
}

ludeKing · 05-30-2004, 08:32 PM

Thankyou, that worked, I should have got that... but it was late last night!