Java constructor question

[suryad]

So I got a Java constructor question...suppose I am creating a gui thru a constructor like so:

public EmailFrame()
{
// SETS UP THE UI HERE
}

Now I am required to create a similar gui but with certain fields different...like the window title of the frame for example and so I create a constructor like so:

public EmailFrame(String windowTitle)
{
// SETS UP THE UI HERE + THE CODE FOR THE TITLE

So now we have a bad programming situation here. I have a default constructor that does not take any arguments but the code is similar to the other constructor that DOES take an argument and everything is the exact same other than the one line that deals with the window title. How do I go about so that I dont have to re-call the code of the first constructor with minimal work? I have some ideas but before I try I would like to receive some feedback. Thanks in advance.

[streetster]

Could you have something like

public EmailFrame()
{
EmailFrame("Default Window Title Goes Here")
}

or

public EmailFrame()
{
this("Default Window Title Goes Here")
}

type thing to avoid code replication? There's prolly much better ways, compared to my javaq noob skills...

[Kezzer]

Well i would've said to overload the constructor but obviously that's going to cause code replication. You could do it as follows:

public EmailFrame() {
setTitle("Default");
createUI(); // this method invokes the UI
}

public EmailFrame(String title) {
setTitle(title);
createUI();
}

When you're extending the JFrame class for example, in the constructor, everything will apply to the parent frame so you can simply do setTitle() and then do whatever you want in another method

[yamangman]

Could you take a boolean value as an argument and then nest the JFrame title in an if..else

if(!true)
super("Window title one");
else
super("Window title two");

[suryad]

Thanks guys for all the replies. I agree with all of your suggestions. I have a complicated little gui going on here...and if you guys are interested just let me know and I can email you guys my code. I am gonna go with Kezzer's suggestion as of now because I do have a lot of code in the constructors that are being replicated. So I am going to take the common code and put it in a function as was suggested and then tweak from there on. Once again your help is highly appreciated. Take care guys.

[Kezzer]

overloading and putting common code into methods is usually the best idea

[suryad]

The following listings are the 2 constructors I am using as of now to make everything work.

Constructor 1:

    public EmailFrame()
    {
        openFrameCount++;
        setTitle("Email Message " + openFrameCount);
        
        JPanel top = new JPanel();
        top.setBorder(new EmptyBorder(10, 10, 10, 10));
        top.setLayout(new BorderLayout());
        top.add(buildAddressPanel(), BorderLayout.NORTH);
        
        content = new JTextArea( 15, 30 );
        content.setBorder( new EmptyBorder(0,5 ,0, 5) );
        content.setLineWrap(true);
        
        JScrollPane textScroller = new JScrollPane(content, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED );
        top.add( textScroller, BorderLayout.CENTER);
        
        JButton sendBtn = new JButton("Send");
        top.add(sendBtn, BorderLayout.SOUTH);
        
        sendBtn.addActionListener(new java.awt.event.ActionListener()
        {
            public void actionPerformed(java.awt.event.ActionEvent evt)
            {
                sendBtnItemActionPerformed(evt);
            }
        });
        
        setContentPane(top);
        pack();
    }

Constructor 2:

 public EmailFrame(String emailToField, String subjField, String bodytext)
    {
         openFrameCount++;
        setTitle("Email Message " + openFrameCount);
        
        JPanel top = new JPanel();
        top.setBorder(new EmptyBorder(10, 10, 10, 10));
        top.setLayout(new BorderLayout());
        top.add(buildAddressPanel(), BorderLayout.NORTH);
        
        toField.setText(emailToField);    // Extra
        toField.setEditable(false);     // Extra
        subField.setText(subjField);    // Extra
        subField.setEditable(false);     // Extra
        
        content = new JTextArea( 15, 30 );
        content.setBorder( new EmptyBorder(0,5 ,0, 5) );
        content.setLineWrap(true);
        content.setText(bodytext);
        
        JScrollPane textScroller = new JScrollPane(content, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED );
        top.add( textScroller, BorderLayout.CENTER);
        
        JButton sendBtn = new JButton("Send");
        top.add(sendBtn, BorderLayout.SOUTH);
        
        sendBtn.addActionListener(new java.awt.event.ActionListener()
        {
            public void actionPerformed(java.awt.event.ActionEvent evt)
            {
                sendBtnItemActionPerformed(evt);
            }
        });
        
        setContentPane(top);
        pack();
    }

The lines marked extra are the lines that are different. So the idea is to have the lowest common denominator in one constructor and the mods in the rest. The only way I can think of by achieving this is by doing:

Public EmailFrame()
{
    initGUIComponents(); // dump gui code here
}

And the second constructor would be:

Public EmailFrame()
{
    initGUIComponents(); // dump gui code here
// the lines of code that are commented as extra 
}

Is that right Kezzer? That what you would recommend?

[Kezzer]

Yup, what you put below looks fine although you didn't include the parameters you were going to include in the constructor in the last example i presume?

[suryad]

Yes thats correct. Thanks a lot.

[Sam]

Leave the set up code in the constructor and create a method called resetGui() or something to set up the defaults on it.

Then call this() on your constructor as Kezzer suggested.