Java packages / statsic problem - Please help!

[brendan_1986]

Hello,

I am writing a chat client. It has about 10 .java files so far. The problem is how to access variables, and such without having to turn everything static, which people keep saying is bad.

I have a MainClass.java file, a ChatConnection.java file, and a StatusWindow.class. How would I access the variables on StatusWindow.java from anoter file without having to put the static keyword in front of it. I do this:

In the ParentFrame (MDI) I have: statusWindow instance. I then need to access the statusWindow.append() method, but without making it static. I hope that makes sense. I have tried using a package, that is putting package name; before each file and then using import name.*; But I still cannot access any of those variables without making the statusWindow variables static.

[Fubarable]

One way to solve this would be to pass references of one object to another. So if a Foo object needs to call the append method of your StatusWindow then pass the StatusWindow object into the Foo object via a method such as setStatusWindow(StatusWindow myStatusWindow) and set a field with the object passed in via the parameter.

[brendan_1986]

But surely when I put package name; in front of every file, set the classpath and then do import name.*;, I'd have access to all those variables? How do you property access methods of a class without making everything static. It's difficult. Or is it okay to change a few of the required vars to static?

[Fubarable]

But surely when I put package name; in front of every file, set the classpath and then do import name.*;, I'd have access to all those variables? How do you property access methods of a class without making everything static. It's difficult. Or is it okay to change a few of the required vars to static?

Clearly you don't as the need for many static variables is a flag for a broken design and a likely need to re-design the application. Your goal is to have each object managing its own behaviors as much as possible and communicating only essential information or messages to other objects that are concerned with their own behaviors and data. Two fundamental concepts of object oriented programming including encapsulation -- avoiding the unnecessary exposure of data, and decoupling -- the separation of groups of data and behaviors into their own units, as isolated from others as possible.

[NeuroFuzzy]

The correct way of doing this would be passing instances of those classes in the constructor, and adding get() methods.

If you have multiple instances of one object, making the objects static isn't even an option.

I don't think you have your head straight about what "static" means. You don't have access to all the variables if you've imported the file because you haven't created an instance of the class yet. Java is an Object Oriented language!

[brendan_1986]

Okay, thanks for the quick replies.Here is my question, a bit simplfied.

I have a class called ParentFrame declared in this class is StatusWindow statusWindow. How do I access the append method of the statusWindow instance, from a different file. If I do: statusWindow.append() it says cannot find variable statusWindow, How can I access that casas instance?

[Fubarable]

Okay, thanks for the quick replies.Here is my question, a bit simplfied.

I have a class called ParentFrame declared in this class is StatusWindow statusWindow. How do I access the append method of the statusWindow instance, from a different file. If I do: statusWindow.append() it says cannot find variable statusWindow, How can I access that casas instance?

Again to repeat what I said before and what neurofuzzy is saying, one way is to pass a reference of the StatusWindow object into the class that needs to call the method.

[milovan]

Do I understand it right? You set:

StatusWindow statusWindow = new StatusWindow();
statusWindow.append();

and it won't work?

[doomsword2001]

do some research on the mvc pattern

1) controller holds the listeners
2) when user does something a listener is called in the controller
3) controller calls a method in model to change its data
4) model notifies the view that it changed
5) view updates it self

i had a badly coded program with statics everywhere i changed it to a nice OO program this way. Thats the point where you learn to design before coding. If you don't have an initial plan you will probably create ugly code which at some stage will cause bugs & headaches & waste of time on debugging.

[brendan_1986]

Do I understand it right? You set:

StatusWindow statusWindow = new StatusWindow();
statusWindow.append();

and it won't work?

statusWindow is in the ParentFrame class. I am trying to call append outside of the classit's decalred in. If I do ParentFrame.statusWindow.append() it requires it to be a static declaration. If I was calling append in the above example, it would work but I need to access it outside of the class it's declared in.

// ParentFrame.java
StatusWindow window;

...

// Connection.java
window.append("connecting .."); // 'cannot find symbol window'..

[quad64bit]

So you have some class A and inside you have some class B. You want to access B from some class C? Is that correct?

If thats the case, you can add an accessor method to A. It can either return B directly, or it can forward information to and from B without show B to C directly. Make sense?

[brendan_1986]

So you have some class A and inside you have some class B. You want to access B from some class C? Is that correct?

If thats the case, you can add an accessor method to A. It can either return B directly, or it can forward information to and from B without show B to C directly. Make sense?

thanks. Yes that is exactly what am I am doing. I will elarn what accessor methods are. thank all.

[quad64bit]

Its quite simple really - based on my example, it might look something like this:

public class A{
    private B b;

    public A(){
        b = new B();
    }

    public B getB(){
        return b;
    }

    class B{
        int number;
        public int getNumber(){
            return number;
        }

        public void setNumber(int number){
            this.number = number;
        }
    }
}


public class C{
    private A a;

    public C(){
        a = new A();
        //Get access to b
        B b = a.getB();
        //get a value from b
        int x = b.getNumber();
        //Access something from B anonymously
        a.getB().setNumber(55);
    }
}

In the above example, A contains the definition for B. A also contains an instance of B. the method in A called getB() returns a reference to B. Outside classes that have access to A can get access to B through this method. It is an accessor method (a getter).

B also contains accessors - setNumber() (a setter), and getNumber() (a getter). Any method that allows you to set something or get something is an accessor by definition. Does this code help make it clear?

[brendan_1986]

Thanks for your example, I understand what you're saying now. I will post back to let you know how it's going.

[quad64bit]

Good Luck! :D