Variable Reference

[waynew]

Hello, I'm new to OOP and Java and I have a problem I have been unable to solve.
I have searched many books and online and can't seem to find a solution that works.
Hoping someone here can enlighten me as to what I am doing wrong.

I have some user preferences in a desktop application that I want to be able to
access from several classes in my package.
Specifically, I need to set some variables in a class then access the values from other classes.
Here is a representation of what I am trying to do:

public class A { // the setup class, initialize and set the variable value
       
        private String aString = "";

        public A {
        }

        public void setAString(String aString) {
            this.aString = aString;
        }

        public String getAString() {
            return aString;
        }

        public void initString() { // actually reads the value from a file in my code
          aString = "abc";
        }
}

public class B { // try to initialize the variable and get the value from class A

        public initVar() {
                A a = new A();
                a.initString(); // makes class A set the variable value  (read the file in my code)
        }

        public doSomething() {
                //get the variable value from class A
                String newString = a.getString(); // returns null from class A
        }
}

Why does a.getString in doSomething return null instead of "abc"?
What do I need to change?
Thanks if you can help!

[Belisarius]

I'm surprised that even compiles - in class B you don't define "a" either in the class of the "doSomething" method - you only define it in "initVar";

Try putting

A a = new A();

in the class scope - I'm willing to bet you won't get null anymore.

[waynew]

Thanks for your help. Yep, it was probably a bad example.
I have since solved the overall problem by using a SingletonObject and it is working fine.

[Belisarius]

Glad you were able to find a solution. Yes, a singleton design pattern is generally the best way to go for configuration objects. Usually I'm quicker at responding to help requests - if you encounter any more difficulty feel free to stop by.

[waynew]

Well then, I have another, unrelated Java question, being a real newbie.
I need to add the ability to my desktop application to capture an RTP audio stream and also to generate an RTP audio stream to transmit.

Can I do this without having to use JMF?

[Belisarius]

Well, that's really not a "newbie" question. No harm in asking - it's just that the solution might be a bit more advanced than you're willing to tackle. I hadn't heard of either of those acronyms before, but poking around a bit it looks like your plan to try and cut out JMF is a good one. Wikipedia mentions several alternatives, but you'd need to investigate them and see if any of them meet your needs.

[waynew]

Well since this is my first Java program, anything I don't know seems like a newbie question.
I have been researching the Sun docs and the forums, including posting a question in the Sun Media forum, but no luck so far.
It looks simpler to use the Sound api as JMF is just more overhead than I need and I am concerned about cross-platform limitations in JMF.
Thanks for your suggestion. I'll keep looking and at last resort, just code it using Sound and see if it works.