Passing arraylist between constructors?

Question

Hi guys,
I've pretty new to java, and I think i'm having a little trouble
understanding scope. The program I'm working on is building a jtree
from an xml file, to do this an arraylist (xmlText) is being built and
declared in the function Main. It's then called to an overloaded
constructor which processes the XML into a jtree:
public Editor( String title, ArrayList xmlText ) throws
ParserConfigurationException
Later, in the second constructor which builds my GUI, I try and call
the same arraylist so I can parse this XML into a set of combo boxes,
but get an error thrown up at me that i'm having a hard time solving- :
public Editor( String title ) throws ParserConfigurationException
// additional code
// Create a read-only combobox- where I get an error.
String [] items = (String []) xmlText.toArray (new String[
xmlText.size () ]);
JComboBox queryBox = new JComboBox(items);
JComboBox queryBox2 = new JComboBox(items);
JComboBox queryBox3 = new JComboBox(items);
JComboBox queryBox4 = new JComboBox(items);
JComboBox queryBox5 = new JComboBox(items);
This is the way I understand the Arraylist can be converted to a string
to use in the combo boxs. However I get an error thrown up at me here
at about line 206, which as far as I understand, is because when the
overloaded constructor calls the other constructor:
public Editor( String title ) throws ParserConfigurationException -
It does not pass in the variable xmlText.
I'm told that the compiler complains because xmlText is not defined
at that point:
- it is not a global variable or class member
- it has not been passed into the function
and
- it has not been declared inside the current function
Can anyone think of a solution to this problem? As I say a lot of this
stuff is still fairly beyond me, I understand the principles behind the
language and the problem, but the solution has been evading me so far.
If anyone could give me any help or a solution here I'd be very
grateful- I'm getting totally stressed over this.
The code I'm working on is below, I've highlighted where the error
crops up too- it's about line 200-206 area. Sorry for the length, I was
unsure as to how much of the code I should post.
public class Editor extends JFrame implements ActionListener
// This is the XMLTree object which displays the XML in a JTree
private XMLTree XMLTree;
private JTextArea textArea, textArea2, textArea3;
// One JScrollPane is the container for the JTree, the other is for
the textArea
private JScrollPane jScroll, jScrollRt, jScrollUp,
jScrollBelow;
private JSplitPane splitPane, splitPane2;
private JPanel panel;
// This JButton handles the tree Refresh feature
private JButton refreshButton;
// This Listener allows the frame's close button to work properly
private WindowListener winClosing;
private JSplitPane splitpane3;
// Menu Objects
private JMenuBar menuBar;
private JMenu fileMenu;
private JMenuItem newItem, openItem, saveItem,
exitItem;
// This JDialog object will be used to allow the user to cancel an exit
command
private JDialog verifyDialog;
// These JLabel objects will be used to display the error messages
private JLabel question;
// These JButtons are used with the verifyDialog object
private JButton okButton, cancelButton;
private JComboBox testBox;
// These two constants set the width and height of the frame
private static final int FRAME_WIDTH = 600;
private static final int FRAME_HEIGHT = 450;
* This constructor passes the graphical construction off to the
overloaded constructor
* and then handles the processing of the XML text
public Editor( String title, ArrayList xmlText ) throws
ParserConfigurationException
this( title );
textArea.setText( ( String )xmlText.get( 0 ) + "\n" );
for ( int i = 1; i < xmlText.size(); i++ )
textArea.append( ( String )xmlText.get( i ) + "\n" );
try
XMLTree.refresh( textArea.getText() );
catch( Exception ex )
String message = ex.getMessage();
System.out.println( message );
}//end try/catch
} //end Editor( String title, String xml )
* This constructor builds a frame containing a JSplitPane, which in
turn contains two
JScrollPanes.
* One of the panes contains an XMLTree object and the other contains
a JTextArea object.
public Editor( String title ) throws ParserConfigurationException
// This builds the JFrame portion of the object
super( title );
Toolkit toolkit;
Dimension dim, minimumSize;
int screenHeight, screenWidth;
// Initialize basic layout properties
setBackground( Color.lightGray );
getContentPane().setLayout( new BorderLayout() );
// Set the frame's display to be WIDTH x HEIGHT in the middle of
the screen
toolkit = Toolkit.getDefaultToolkit();
dim = toolkit.getScreenSize();
screenHeight = dim.height;
screenWidth = dim.width;
setBounds( (screenWidth-FRAME_WIDTH)/2,
(screenHeight-FRAME_HEIGHT)/2, FRAME_WIDTH,
FRAME_HEIGHT );
// Build the Menu
// Build the verify dialog
// Set the Default Close Operation
// Create the refresh button object
// Add the button to the frame
// Create two JScrollPane objects
jScroll = new JScrollPane();
jScrollRt = new JScrollPane();
// First, create the JTextArea:
// Create the JTextArea and add it to the right hand JScroll
textArea = new JTextArea( 200,150 );
jScrollRt.getViewport().add( textArea );
// Next, create the XMLTree
XMLTree = new XMLTree();
XMLTree.getSelectionModel().setSelectionMode(
TreeSelectionModel.SINGLE_TREE_SELECTION
XMLTree.setShowsRootHandles( true );
// A more advanced version of this tool would allow the JTree to
be editable
XMLTree.setEditable( false );
// Wrap the JTree in a JScroll so that we can scroll it in the
JSplitPane.
jScroll.getViewport().add( XMLTree );
// Create the JSplitPane and add the two JScroll objects
splitPane = new JSplitPane( JSplitPane.HORIZONTAL_SPLIT, jScroll,
jScrollRt );
splitPane.setOneTouchExpandable(true);
splitPane.setDividerLocation(200);
jScrollUp = new JScrollPane();
jScrollBelow=new JScrollPane();
// Here is were the error is coming up
String [] items = (String []) xmlText.toArray (new String[
xmlText.size () ]);
JComboBox queryBox = new JComboBox(items);
JComboBox queryBox2 = new JComboBox(items);
JComboBox queryBox3 = new JComboBox(items);
JComboBox queryBox4 = new JComboBox(items);
JComboBox queryBox5 = new JComboBox(items);
* I'm adding the scroll pane to the split pane,
* a panel to the top of the split pane, and some uneditible
combo boxes
* to them. Then I'll rearrange them to rearrange them, but
unfortunately am getting an error thrown up above.
panel = new JPanel();
panel.add(queryBox);
panel.add(queryBox2);
panel.add(queryBox3);
panel.add(queryBox4);
panel.add(queryBox5);
jScrollUp.getViewport().add( panel );
// Now building a text area
textArea3 = new JTextArea(200, 150);
jScrollBelow.getViewport().add( textArea3 );
splitPane2 = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
jScrollUp, jScrollBelow);
splitPane2.setPreferredSize( new Dimension(300, 200) );
splitPane2.setDividerLocation(100);
splitPane2.setOneTouchExpandable(true);
// in here can change the contents of the split pane
getContentPane().add(splitPane2,BorderLayout.SOUTH);
// Provide minimum sizes for the two components in the split pane
minimumSize = new Dimension(200, 150);
jScroll.setMinimumSize( minimumSize );
jScrollRt.setMinimumSize( minimumSize );
// Provide a preferred size for the split pane
splitPane.setPreferredSize( new Dimension(400, 300) );
// Add the split pane to the frame
getContentPane().add( splitPane, BorderLayout.CENTER );
//Put the final touches to the JFrame object
validate();
setVisible(true);
// Add a WindowListener so that we can close the window
winClosing = new WindowAdapter()
public void windowClosing(WindowEvent e)
verifyDialog.show();
addWindowListener(winClosing);
} //end Editor()
* When a user event occurs, this method is called. If the action
performed was a click
* of the "Refresh" button, then the XMLTree object is updated using
the current XML text
* contained in the JTextArea
public void actionPerformed( ActionEvent ae )
if ( ae.getActionCommand().equals( "Refresh" ) )
try
XMLTree.refresh( textArea.getText() );
catch( Exception ex )
String message = ex.getMessage();
ex.printStackTrace();
}//end try/catch
else if ( ae.getActionCommand().equals( "OK" ) )
exit();
else if ( ae.getActionCommand().equals( "Cancel" ) )
verifyDialog.hide();
}//end if/else if
} //end actionPerformed()
// Program execution begins here. An XML file (*.xml) must be passed
into the method
public static void main( String[] args )
String fileName = "";
BufferedReader reader;
String line;
ArrayList xmlText = null;
Editor Editor;
// Build a Document object based on the specified XML file
try
if( args.length > 0 )
fileName = args[0];
if ( fileName.substring( fileName.indexOf( '.' ) ).equals(
".xml" ) )
reader = new BufferedReader( new FileReader( fileName )
xmlText = new ArrayList();
while ( ( line = reader.readLine() ) != null )
xmlText.add( line );
} //end while ( ( line = reader.readLine() ) != null )
// The file will have to be re-read when the Document
object is parsed
reader.close();
// Construct the GUI components and pass a reference to
the XML root node
Editor = new Editor( "Editor 1.0", xmlText );
else
help();
} //end if ( fileName.substring( fileName.indexOf( '.' )
).equals( ".xml" ) )
else
Editor = new Editor( "Editor 1.0" );
} //end if( args.length > 0 )
catch( FileNotFoundException fnfEx )
System.out.println( fileName + " was not found." );
exit();
catch( Exception ex )
ex.printStackTrace();
exit();
}// end try/catch
}// end main()
// A common source of operating instructions
private static void help()
System.out.println( "\nUsage: java Editor filename.xml" );
System.exit(0);
} //end help()
// A common point of exit
public static void exit()
System.out.println( "\nThank you for using Editor 1.0" );
System.exit(0);
} //end exit()
class newMenuHandler implements ActionListener
public void actionPerformed( ActionEvent ae )
textArea.setText( "" );
try
// Next, create a new XMLTree
XMLTree = new XMLTree();
XMLTree.getSelectionModel().setSelectionMode(
TreeSelectionModel.SINGLE_TREE_SELECTION );
XMLTree.setShowsRootHandles( true );
// A more advanced version of this tool would allow the JTree
to be editable
XMLTree.setEditable( false );
catch( Exception ex )
String message = ex.getMessage();
ex.printStackTrace();
}//end try/catch
}//end actionPerformed()
}//end class newMenuHandler
class openMenuHandler implements ActionListener
JFileChooser jfc;
Container parent;
int choice;
openMenuHandler()
super();
jfc = new JFileChooser();
jfc.setSize( 400,300 );
jfc.setFileFilter( new XmlFileFilter() );
parent = openItem.getParent();
}//end openMenuHandler()
public void actionPerformed( ActionEvent ae )
// Displays the jfc and sets the dialog to 'open'
choice = jfc.showOpenDialog( parent );
if ( choice == JFileChooser.APPROVE_OPTION )
String fileName, line;
BufferedReader reader;
fileName = jfc.getSelectedFile().getAbsolutePath();
try
reader = new BufferedReader( new FileReader( fileName ) );
textArea.setText( reader.readLine() + "\n" );
while ( ( line = reader.readLine() ) != null )
textArea.append( line + "\n" );
} //end while ( ( line = reader.readLine() ) != null )
// The file will have to be re-read when the Document
object is parsed
reader.close();
XMLTree.refresh( textArea.getText() );
catch ( Exception ex )
String message = ex.getMessage();
ex.printStackTrace();
}//end try/catch
jfc.setCurrentDirectory( new File( fileName ) );
} //end if ( choice == JFileChooser.APPROVE_OPTION )
}//end actionPerformed()
}//end class openMenuHandler
class saveMenuHandler implements ActionListener
JFileChooser jfc;
Container parent;
int choice;
saveMenuHandler()
super();
jfc = new JFileChooser();
jfc.setSize( 400,300 );
jfc.setFileFilter( new XmlFileFilter() );
parent = saveItem.getParent();
}//end saveMenuHandler()
public void actionPerformed( ActionEvent ae )
// Displays the jfc and sets the dialog to 'save'
choice = jfc.showSaveDialog( parent );
if ( choice == JFileChooser.APPROVE_OPTION )
String fileName;
File fObj;
FileWriter writer;
fileName = jfc.getSelectedFile().getAbsolutePath();
try
writer = new FileWriter( fileName );
textArea.write( writer );
// The file will have to be re-read when the Document
object is parsed
writer.close();
catch ( IOException ioe )
ioe.printStackTrace();
}//end try/catch
jfc.setCurrentDirectory( new File( fileName ) );
} //end if ( choice == JFileChooser.APPROVE_OPTION )
}//end actionPerformed()
}//end class saveMenuHandler
class exitMenuHandler implements ActionListener
public void actionPerformed( ActionEvent ae )
verifyDialog.show();
}//end actionPerformed()
}//end class exitMenuHandler
class XmlFileFilter extends javax.swing.filechooser.FileFilter
public boolean accept( File fobj )
if ( fobj.isDirectory() )
return true;
else
return fobj.getName().endsWith( ".xml" );
}//end accept()
public String getDescription()
return "*.xml";
}//end getDescription()
}//end class XmlFileFilter
} //end class Editor
Sorry if this post has been a bit lengthy, any help you guys could give
me solving this would be really appreciated.
Thanks,
Iain.

Answer 1

Hey. Couple pointers:
When posting, try to keep code inbetween code tags (button between spell check and quote original). It will pretty-print the code.
Posting code is good. Usually, though, you want to post theminimum amount of code which runs and shows your problem.
That way people don't have to wade through irrelevant stuff and
they have an easier time helping.
http://homepage1.nifty.com/algafield/sscce.html
As for your problem, this is a scope issue. You declare an
ArrayList xmlText in main(). That means that everywhere after
the declaration in main(), you can reference your xmlText.
So far so good. Then, inside main(), you call
Editor = new Editor( "Editor 1.0", xmlText );Now you've passed the xmlText variable to a new method,
Editor(String title, ArrayList xmlText) [which happens to be a
constructor, but that's not important]. When you do that, you
make the two variables title and xmlText available to the whole
Editor(String, ArrayList) method.
This is where you get messed up. You invoke another method
from inside Editor(String, ArrayList). When you call
this(title);you're invoking the method Editor(String title). You aren't passing
in your arraylist, though. You've got code in the Editor(String) method
which is trying to reference xmlText, but you'd need to pass in
your ArrayList in order to do so.
My suggestion would be to merge the two constructor methods into
one, Editor(String title, ArrayList xmlText).