Creating one class from another

[Craig Boyd]

Hello All,

I have a SIMPLE JFrame class and a SIMPLE JMenuBar class. I want the JFrame class to call/instantiate the JMenuBar that I have written, but I don't think I have the JMenuBar set up right. I get the following two errors when I try to compile it:

C:\Projects\Java\MyMenuBar.java:67: invalid method declaration; return type required
     Return(menuBar);
     ^
C:\Projects\Java\MyMenuBar.java:67: <identifier> expected
     Return(menuBar);
                   ^

Here is the code for MyMenuBar.java:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyMenuBar {

	public JMenuBar main() {

	// Creates a menubar for a JFrame
        JMenuBar menuBar = new JMenuBar();

	// Define and add two drop down menu to the menubar
        JMenu submenu = new JMenu("SubMenu");
        JMenu fileMenu = new JMenu("File");
        JMenu editMenu = new JMenu("Edit");
        menuBar.add(fileMenu);
        menuBar.add(editMenu);

        // Create and add simple menu item to one of the drop down menu
        JMenuItem newAction = new JMenuItem("New");
        JMenuItem openAction = new JMenuItem("Open");
        JMenuItem exitAction = new JMenuItem("Exit");
        JMenuItem cutAction = new JMenuItem("Cut");
        JMenuItem copyAction = new JMenuItem("Copy");
        JMenuItem pasteAction = new JMenuItem("Paste");
        JMenuItem subMenuItem1 = new JMenuItem("Sub-Item");

	// Create and add CheckButton as a menu item to one of the drop down
        // menu
        JCheckBoxMenuItem checkAction = new JCheckBoxMenuItem("Check Action");

        // Create and add Radio Buttons as simple menu items to one of the drop
        // down menu
        JRadioButtonMenuItem radioAction1 = new JRadioButtonMenuItem(
                "Radio Button1");
        JRadioButtonMenuItem radioAction2 = new JRadioButtonMenuItem(
                "Radio Button2");

        // Create a ButtonGroup and add both radio Button to it. Only one radio
        // button in a ButtonGroup can be selected at a time.
        ButtonGroup bg = new ButtonGroup();
        bg.add(radioAction1);
        bg.add(radioAction2);
        fileMenu.add(newAction);
        fileMenu.add(openAction);
        fileMenu.add(checkAction);
        fileMenu.addSeparator();
        fileMenu.add(exitAction);
        editMenu.add(cutAction);
        editMenu.add(copyAction);
        editMenu.add(pasteAction);
        editMenu.addSeparator();
        editMenu.add(radioAction1);
        editMenu.add(radioAction2);
        submenu.add(subMenuItem1);
	editMenu.add(submenu);

        // Add a listener to the New menu item. actionPerformed() method will
        // invoked, if user triggred this menu item

		newAction.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                System.out.println("You have clicked on the new action");
            }
        });
     }
     Return(menuBar);
  }

What am I doing wrong?

Thanks,

Craigbert

[Joanne Neal]

Java is case sensitive. Try return

[Craig Boyd]

Joanne, thanks for the reply. I made the change and now I am getting:

C:\Projects\Java\MyMenuBar.java:67: illegal start of type
     return(menuBar);
     ^
C:\Projects\Java\MyMenuBar.java:67: <identifier> expected
     return(menuBar);
                   ^

[Joanne Neal]

That often suggests your {} are not matching up somewhere. Make sure you haven't got an extra one somewhere or you're not are missing a closing one and that they are all where you intended them to be.

Edit: Or you can just wait for Stephan to tell you where the problem is

[Stephan van Hulst]

Your return statement is outside your method.

[Craig Boyd]

Well, that solved that problem! Thanks!
Now when I try to compile the JFrame I get this error:

C:\Projects\Java\MyJFrame.java:16: cannot find symbol
symbol  : method MyMenuBar()
location: class MyJFrame
        frame.setJMenuBar(MyMenuBar());
                          ^

Here is the code for MyJFrame:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyJFrame {

	public static void main(String s[]) {
		JFrame frame = new JFrame("My Beginning JFrame");
		frame.setLocation(600,300);
		Dimension minSize = new Dimension(400,200);
		frame.setMinimumSize(minSize);



		// Add the menubar to the frame
               frame.setJMenuBar(MyMenuBar());



		// Add a window listner for close button
		frame.addWindowListener(new WindowAdapter() {

			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});

		frame.pack();
		frame.setVisible(true);
	}
}

Am I not calling the MyMenuBar correctly?

Thanks,

Craigbert

[Matthew Brown]

Craig Boyd wrote:Am I not calling the MyMenuBar correctly?

I assume you're trying to create a new one? Then you need a "new".

frame.setJMenuBar(new MyMenuBar());

Edit: although that still won't work, since MyMenuBar isn't a JMenuBar.

So you can either do this:

frame.setJMenuBar(new MyMenuBar().main());

Or, and I think this is more sensible, have MyMenuBar extend JMenuBar, and swap your main() method for a constructor. For example:

public class MyMenuBar extends JMenuBar {  
    public MyMenuBar() {  
        // Define and add two drop down menu to the menubar  
        JMenu submenu = new JMenu("SubMenu");  
        JMenu fileMenu = new JMenu("File");  
        JMenu editMenu = new JMenu("Edit");  
        this.add(fileMenu);  
        this.add(editMenu); 
        // etc... 

[Craig Boyd]

OK...everything compiles and runs, but the menu bar does not appear in the JFrame.

I took the "extends" approach Matthew suggested.

Why would the menu bar not appear?

Thanks,

Craig Boyd

[Darryl Burke]

To get better help sooner, post a SSCCE (Short, Self Contained, Compilable and Executable) example that demonstrates the problem.

[Craig Boyd]

Fair enough. I can not seem to find the right file extension to use so I am including the code for both here. They are both VERY small.
They both compile and run w/the exception of the menu bar not showing up.
MyJFrame.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyJFrame {

	public static void main(String s[]) {
		JFrame frame = new JFrame("My Beginning JFrame");
		frame.setLocation(600,300);
		Dimension minSize = new Dimension(400,200);
		frame.setMinimumSize(minSize);



		// Add the menubar to the frame
        frame.setJMenuBar(new MyMenuBar());



		// Add a window listner for close button
		frame.addWindowListener(new WindowAdapter() {

			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	// This is an empty content area in the frame

		frame.pack();
		frame.setVisible(true);
	}
}

MyMenuBar.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyMenuBar extends JMenuBar {

	public JMenuBar main() {

	// Creates a menubar for a JFrame
        JMenuBar menuBar = new JMenuBar();

	// Define and add two drop down menu to the menubar
        JMenu submenu = new JMenu("SubMenu");
        JMenu fileMenu = new JMenu("File");
        JMenu editMenu = new JMenu("Edit");
        menuBar.add(fileMenu);
        menuBar.add(editMenu);

        // Create and add simple menu item to one of the drop down menu
        JMenuItem newAction = new JMenuItem("New");
        JMenuItem openAction = new JMenuItem("Open");
        JMenuItem exitAction = new JMenuItem("Exit");
        JMenuItem cutAction = new JMenuItem("Cut");
        JMenuItem copyAction = new JMenuItem("Copy");
        JMenuItem pasteAction = new JMenuItem("Paste");
        JMenuItem subMenuItem1 = new JMenuItem("Sub-Item");

	// Create and add CheckButton as a menu item to one of the drop down
        // menu
        JCheckBoxMenuItem checkAction = new JCheckBoxMenuItem("Check Action");

        // Create and add Radio Buttons as simple menu items to one of the drop
        // down menu
        JRadioButtonMenuItem radioAction1 = new JRadioButtonMenuItem(
                "Radio Button1");
        JRadioButtonMenuItem radioAction2 = new JRadioButtonMenuItem(
                "Radio Button2");

        // Create a ButtonGroup and add both radio Button to it. Only one radio
        // button in a ButtonGroup can be selected at a time.
        ButtonGroup bg = new ButtonGroup();
        bg.add(radioAction1);
        bg.add(radioAction2);
        fileMenu.add(newAction);
        fileMenu.add(openAction);
        fileMenu.add(checkAction);
        fileMenu.addSeparator();
        fileMenu.add(exitAction);
        editMenu.add(cutAction);
        editMenu.add(copyAction);
        editMenu.add(pasteAction);
        editMenu.addSeparator();
        editMenu.add(radioAction1);
        editMenu.add(radioAction2);
        submenu.add(subMenuItem1);
	    editMenu.add(submenu);

        // Add a listener to the New menu item. actionPerformed() method will
        // invoked, if user triggred this menu item

		newAction.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                System.out.println("You have clicked on the new action");
            }
        });
        return(menuBar);
     }

  }

Thanks,

Craigbert

[Matthew Brown]

You haven't actually done what I suggested. You've made MyMenuBar extend JMenuBar, but you haven't made the other changes I said would be necessary:

- change the main() method into a constructor
- add the menus to the MyMenuBar object you're creating, rather than creating another new menu bar and adding them to that.

So the problem at the moment is that two JMenuBars get created. One has all the items added to it, and the other is what you're adding to the JFrame. My last post gave an extract of what needs doing.

[Craig Boyd]

Matthew, thanks for being patient with this green horn.

I think I made all the changes you suggested but now I am getting a different error when I try to compile the MyMenuBar class.

Here is all the code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyMenuBar extends JMenuBar {

	public MyMenuBar() {

	// Creates a menubar for a JFrame
        JMenuBar menuBar = new JMenuBar();

	// Define and add two drop down menu to the menubar
        JMenu submenu = new JMenu("SubMenu");
        JMenu fileMenu = new JMenu("File");
        JMenu editMenu = new JMenu("Edit");
        this.add(fileMenu);
        this.add(editMenu);

        // Create and add simple menu item to one of the drop down menu
        JMenuItem newAction = new JMenuItem("New");
        JMenuItem openAction = new JMenuItem("Open");
        JMenuItem exitAction = new JMenuItem("Exit");
        JMenuItem cutAction = new JMenuItem("Cut");
        JMenuItem copyAction = new JMenuItem("Copy");
        JMenuItem pasteAction = new JMenuItem("Paste");
        JMenuItem subMenuItem1 = new JMenuItem("Sub-Item");

	// Create and add CheckButton as a menu item to one of the drop down
        // menu
        JCheckBoxMenuItem checkAction = new JCheckBoxMenuItem("Check Action");

        // Create and add Radio Buttons as simple menu items to one of the drop
        // down menu
        JRadioButtonMenuItem radioAction1 = new JRadioButtonMenuItem(
                "Radio Button1");
        JRadioButtonMenuItem radioAction2 = new JRadioButtonMenuItem(
                "Radio Button2");

        // Create a ButtonGroup and add both radio Button to it. Only one radio
        // button in a ButtonGroup can be selected at a time.
        ButtonGroup bg = new ButtonGroup();
        bg.add(radioAction1);
        bg.add(radioAction2);
        fileMenu.add(newAction);
        fileMenu.add(openAction);
        fileMenu.add(checkAction);
        fileMenu.addSeparator();
        fileMenu.add(exitAction);
        editMenu.add(cutAction);
        editMenu.add(copyAction);
        editMenu.add(pasteAction);
        editMenu.addSeparator();
        editMenu.add(radioAction1);
        editMenu.add(radioAction2);
        submenu.add(subMenuItem1);
	    editMenu.add(submenu);

        // Add a listener to the New menu item. actionPerformed() method will
        // invoked, if user triggred this menu item

		newAction.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                System.out.println("You have clicked on the new action");
            }
        });
        return(MyMenuBar);
     }

  }

Here is the error:

Java\MyMenuBar.java:66: cannot return a value from method whose result type is void
        return(MyMenuBar);

What n00b error am I committing here?

Thanks,

Craigbert

[Craig Boyd]

OK. I got both classes compiling, but I think I am still creating two instances of the JMenuBar and the one I am getting is not the one I want.
Anyone have any idea where I am going astray?

MyJFrame.java :

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyJFrame {

	public static void main(String s[]) {
		JFrame frame = new JFrame("My Beginning JFrame");
		frame.setLocation(600,300);
		Dimension minSize = new Dimension(400,200);
		frame.setMinimumSize(minSize);

		// Add the menubar to the frame
        frame.setJMenuBar(new MyMenuBar());

		// Add a window listner for close button
		frame.addWindowListener(new WindowAdapter() {

			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	// This is an empty content area in the frame

		frame.pack();
		frame.setVisible(true);
	}
}

MyMenuBar.java :

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyMenuBar extends JMenuBar {

	public JMenuBar menuBar() {

	// Creates a menubar for a JFrame
        JMenuBar menuBar = new JMenuBar();

	// Define and add two drop down menu to the menubar
        JMenu submenu = new JMenu("SubMenu");
        JMenu fileMenu = new JMenu("File");
        JMenu editMenu = new JMenu("Edit");
        this.add(fileMenu);
        this.add(editMenu);

        // Create and add simple menu item to one of the drop down menu
        JMenuItem newAction = new JMenuItem("New");
        JMenuItem openAction = new JMenuItem("Open");
        JMenuItem exitAction = new JMenuItem("Exit");
        JMenuItem cutAction = new JMenuItem("Cut");
        JMenuItem copyAction = new JMenuItem("Copy");
        JMenuItem pasteAction = new JMenuItem("Paste");
        JMenuItem subMenuItem1 = new JMenuItem("Sub-Item");

	// Create and add CheckButton as a menu item to one of the drop down
        // menu
        JCheckBoxMenuItem checkAction = new JCheckBoxMenuItem("Check Action");

        // Create and add Radio Buttons as simple menu items to one of the drop
        // down menu
        JRadioButtonMenuItem radioAction1 = new JRadioButtonMenuItem(
                "Radio Button1");
        JRadioButtonMenuItem radioAction2 = new JRadioButtonMenuItem(
                "Radio Button2");

        // Create a ButtonGroup and add both radio Button to it. Only one radio
        // button in a ButtonGroup can be selected at a time.
        ButtonGroup bg = new ButtonGroup();
        bg.add(radioAction1);
        bg.add(radioAction2);
        fileMenu.add(newAction);
        fileMenu.add(openAction);
        fileMenu.add(checkAction);
        fileMenu.addSeparator();
        fileMenu.add(exitAction);
        editMenu.add(cutAction);
        editMenu.add(copyAction);
        editMenu.add(pasteAction);
        editMenu.addSeparator();
        editMenu.add(radioAction1);
        editMenu.add(radioAction2);
        submenu.add(subMenuItem1);
	    editMenu.add(submenu);

        // Add a listener to the New menu item. actionPerformed() method will
        // invoked, if user triggred this menu item

		newAction.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                System.out.println("You have clicked on the new action");
            }
        });
        return(menuBar);
     }

  }

Thanks,

Craigbert
Certified LVI
(Local Village Idiot)

[Joanne Neal]

You've gone back to how you had it originally (except your main method is now called menuBar).
Change menuBar into a constructor and remove the return statement. Constructors don't return anything.

Also you can remove lines 9 and 10. You don't need to create a JMenuBar.

[Craig Boyd]

THANK YOU Joanne!

That did it!!!

Thanks,

Craigbert
Certified LVI
(Local Village Idiot)