How to declare Variables accessable from every method 1

[aas1611]

Hi,

I need to have a variable that can be accessed from every method in a class.

Here is what I did (the variable called IPAdresse):

public class FrageClient extends JFrame implements ActionListener {
   String IPAdresse;
   ...
   private void createAndShowGUI(int flag) {
      //this method can read the variable entered from main method
      System.out.println("IP: " + IPAdresse);
      ...
   }
   public FrageClient(String begin, String IPAd) {
	IPAdresse = IPAd;
	createAndShowGUI(0);
   }
	
   public static void main (String args[]) {
	new FrageClient("Start", args[0]); // args[0] is the IPAdresse
   }
   public void execute(String Answer) {
        // here is the problem -> IPAdresse comes out null
	System.out.println("IP: " + IPAdresse); 
   }

I run this java code with: java FrageClient 192.100.2.100

How to make my execute method read my IPAdresse?

Thanks for any clue!

Andre

 

[Diancecht]

By convention, method and class names start with non-capital letters.

And what happens between the call to createGUI and the call the execute? I guess there's something you're not telling us.

Cheers,
Dian

 

[aas1611]

I got these method and class names from the book I'm studying from, so do not blame it on me But thanks for the info.

And you're right, I forgot to mention about the actionPerformed method:

public void actionPerformed(ActionEvent ae) {
   Object eventTarget = ae.getSource();
   if (eventTarget==Abschicken){
      strEingabe = Eingabe.getText().toString();
      FrageClient client = new FrageClient();
      client.execute(strEingabe);
   }
   ....
}

In the createAndShowGUI, I have a button called Abschicken, which means "submit", initiated like the following:

Abschicken = new JButton("Abschicken");
Abschicken.addActionListener(this);

So, does it give you a better insight to help me?

Andre

 

[Diancecht]

Sure.

1.- Throw that book away
2.- You're creating two instances of your FrageClient class: one in the main method and another one in the actionPerformed method. The first one receives the IP param, but not the second one.

Cheers,
Dian

 

[aas1611]

Great! You are right, I have two FrageClient instances. Thanks for pointing it out.

While we're at it, I have an input field (an integer) in my GUI. How to make this input number disappear after I click the submit button? Something like refresh method, so the input field is empty again. For now, the number that I just entered stays there after I click submit button.

here is the code in createAndShowGUI:

Eingabe = new JTextField("");
...
workPanel.add(Eingabe);
...
pane.add(BorderLayout.CENTER, workPanel);

Andre

 

[Diancecht]

Add an actionListener to that submit button, and add some code to the actionPerformed method that clears the field value.

Cheers,
Dian

 

[aas1611]

Alright, I'll give it a try. Thanks for you help but I won't throw my book away, though
Is it that bad having a method or class name with capital letter? It doesn't confuse me, and as long as it works, it's fine by me...

Andre

 

[Diancecht]

Yeah, it works, but it's hard to read by another people. A good program doesn't just work, it's reusable and maintainable.

That means other people can see your program, fix it or modify it in a easy way.

Cheers,
Dian