Help me understand how variables work in Java

Question

I am having problems understanding how private and public variables work. I am trying to fill the myStorage.outString variable from myThread. But it seems I cannot see the setInString method from myThread. Here is my example:

public class CT63_Console extends MIDlet {
    public Storage myStorage;
    public void startApp() {
        this.myStorage = new Storage();
    }
}

public class storage{
    private String[] outString;

    public Storage(){
        AClass myThread = new AClass();
        myThread.start();
    }
    public void setInString(String sendString){
        this.outString = sendString; //push seems not to be supported by MIDP
    }
}

public class AClass{
    public void run(){
        myFunction("write this into Storage var outString");
    }

    private myFunction(myString){
        myStorage.setInString(myString);
    }
}

What do I have to do to set the variable and why am I wrong?

Answer 1

You are trying to access myStorage without having a reference to it. You could pass this reference when you create the AClass instance.

Also, you are trying to assign a String to an array of Strings which can't be done.

public class Storage{
    private String outString;

    public Storage(){
        AClass myThread = new AClass(this);
        myThread.start();
    }
    public void setInString(String sendString){
        this.outString = sendString; //push seems not to be supported by MIDP
    }
}

public class AClass {
    Storage myStorage;

    public AClass(Storage s) {
        this.myStorage = s;
    }

    public void run(){
        myFunction("write this into Storage var outString");
    }

    private myFunction(String myString) {
        myStorage.setInString(myString);
    }
}

Answer 2

this.outString = sendString;

outString is an array of strings (String[]). You cannot assign a single string to an array of strings. So either you need to change the type of that variable to a single string (just String), or you need to specify an index where you assign that string to. Note that in the latter case you need to initialize the array first.