Re: Need a little help

Knute Johnson <>
Mon, 05 Feb 2007 08:59:52 -0800
<coJxh.9$%N7.4@newsfe13.lga> wrote:

I am just learning java and need a tiny bit of help. The code below
is a project that I had to create. It works except for one small
part. When I click on the Edit menu and select Insert I am prompted
for the information to add to the arrays. After that it should add
the new record to the JTextPane in order sorted by the artist. For
some reason no matter how I try to sort this it always sorts only the
original data and leaves any new entries at the bottom. Can you see
where I wnet wrong and point me in the right direction to make the
sort work correctly? Thanks.


    Chapter 7: Programming Assignment 2
    Programmer: Richard Glisson
    Date: 4 February 2007
    Purpose: Sample program to show data about musical artists

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

public class MyMusic extends JFrame implements ActionListener
    //construct components
    JLabel sortPrompt = new JLabel("Sort by:");
    JComboBox fieldCombo = new JComboBox();
    JTextPane textPane = new JTextPane();

    //initialize data in the arrays
    String artist[] = {"Chris Tomlin", "David Crowder Band", "Selah",
"Casting Crowns", "Third Day"};
    String genre[] = {"Contemporary Christian", "Contemporary Christian",
"Contemporary Christian", "Contemporary Christian", "Contemporary
    String greatest[] = {"Holy is the Lord", "Here is our King", "All My
Praise", "Voice of Truth", "You Are Mine"};
    String recordLabel[] = {"EMI CMG Publishing", "EMI CMG Publishing",
"BMG Songs", "Club Zoo", "EMI CMG Publishing"};

    //construct an instance of MyMusic
    public MyMusic()
        super("Favorite Music");

    //create the menu system
    public JMenuBar createMenuBar()
        //create an instance of the menu bar
        JMenuBar mnuBar = new JMenuBar();

        //construct and populate the File menu
        JMenu mnuFile = new JMenu("File", true);

        JMenuItem mnuFileExit = new JMenuItem("Exit");

        //construct and populate the Edit Menu
        JMenu mnuEdit = new JMenu("Edit", true);

        JMenuItem mnuEditInsert = new JMenuItem("Insert New Artist");

        JMenu mnuSort = new JMenu("Sort", true);

        JMenuItem mnuSortArtist = new JMenuItem("Sort by Artist");

        JMenuItem mnuSortGenre = new JMenuItem("Sort by Genre");

        JMenuItem mnuSortGreatest = new JMenuItem("Sort by Greatest Hit");

        JMenuItem mnuSortLabel = new JMenuItem("Sort by Record Label");

        return mnuBar;
    }//end public JMenuBar createMenuBar()

    //create the content pane
    public Container createContentPane()
        //create the JTextPane and center panel
        JPanel centerPanel = new JPanel();
            textPane = addTextToTextPane();
            JScrollPane scrollPane = new JScrollPane(textPane);


            scrollPane.setPreferredSize(new Dimension(900, 200));

        //create Container and set attributes
        Container c = getContentPane();
            c.setLayout(new BorderLayout(10, 10));
            c.add(centerPanel, BorderLayout.CENTER);

        return c;

    }//end public Container createContentPane()

    //method to create tab stops and set font styles
    protected void setTabsAndStyles(JTextPane textPane)
        //create Tab Stops
        TabStop[] tabs = new TabStop[4];
            tabs[0] = new TabStop(200, TabStop.ALIGN_LEFT, TabStop.LEAD_NONE);
            tabs[1] = new TabStop(350, TabStop.ALIGN_LEFT, TabStop.LEAD_NONE);
            tabs[2] = new TabStop(500, TabStop.ALIGN_LEFT, TabStop.LEAD_NONE);
            tabs[3] = new TabStop(700, TabStop.ALIGN_LEFT, TabStop.LEAD_NONE);

        TabSet tabset = new TabSet(tabs);

        //set Tab Style
        StyleContext tabStyle = StyleContext.getDefaultStyleContext();
        AttributeSet aset = tabStyle.addAttribute(SimpleAttributeSet.EMPTY,
StyleConstants.TabSet, tabset);
        textPane.setParagraphAttributes(aset, false);

        //set Font Style
        Style fontStyle =

        Style regular = textPane.addStyle("regular", fontStyle);
        StyleConstants.setFontFamily(fontStyle, "SansSerif");

        Style s = textPane.addStyle("italic", regular);
        StyleConstants.setItalic(s, true);

        s = textPane.addStyle("bold", regular);
        StyleConstants.setBold(s, true);

        s = textPane.addStyle("large", regular);
        StyleConstants.setFontSize(s, 16);
    }//end protected void setTabsAndStyles(JTextPane textPane)

    //method to add new text to the JTextPane
    public JTextPane addTextToTextPane()
        Document doc = textPane.getDocument();
            //clear previous text
            doc.remove(0, doc.getLength());

            //insert title
            doc.insertString(0, "ARTIST\tGENRE\tGREATEST HIT\tRECORD LABEL\n",

            //insert detail
            for (int j = 0; j < artist.length; j++)
                doc.insertString(doc.getLength(), artist[j] + "\t",
                doc.insertString(doc.getLength(), genre[j] + "\t",
                doc.insertString(doc.getLength(), greatest[j] + "\t",
                doc.insertString(doc.getLength(), recordLabel[j] + "\n",
        }//end try
        catch (BadLocationException ble)
            System.err.println("Couldn't insert text.");
        return textPane;

    //event to process user clicks
    public void actionPerformed(ActionEvent e)
        String arg = e.getActionCommand();

        //user clicks Exit on the File Menu
        if (arg == "Exit")

        //user clicks Insert New Artist on the Edit Menu
        if (arg == "Insert")
            //accept new data
            String newArtist = JOptionPane.showInputDialog(null, "Please enter
the new Artist's name");
            String newGenre = JOptionPane.showInputDialog(null, "Please enter
the genre");
            String newGreatest = JOptionPane.showInputDialog(null, "Please
enter " + newArtist + "'s greatest hit");
            String newRecordLabel = JOptionPane.showInputDialog(null, "Please
enter " + newArtist + "'s record label");

            //enlarge arrays
            artist = enlargeArray(artist);
            genre = enlargeArray(genre);
            greatest = enlargeArray(greatest);
            recordLabel = enlargeArray(recordLabel);

            //add new data to arrays
            artist[artist.length-1] = newArtist;
            genre[genre.length-1] = newGenre;
            greatest[greatest.length-1] = newGreatest;
            recordLabel[recordLabel.length-1] = newRecordLabel;

            //call sort method

        if (arg == "SortArtist")

        if (arg == "SortGenre")

        if (arg == "SortGreatest")

        if (arg == "SortLabel")

    }//end public void actionPerformed(ActionEvent e)

    //method to enlarge an array by 1
    public String[] enlargeArray(String[] currentArray)
        String[] newArray = new String[currentArray.length + 1];
        for (int i = 0; i < currentArray.length; i++)
            newArray[i] = currentArray[i];
        return newArray;
    }//end public String[] enlargeArray(String[] currentArray)

    //method to sort arrays
    public void sort(String tempArray[])
        //loop to control number of passes
        for (int pass = 1; pass < tempArray.length; pass++)
            for (int element = 0; element < tempArray.length - 1; element++)
                if (tempArray[element].compareTo(tempArray[element + 1]) > 0)
                    swap(artist, element, element + 1);
                    swap(genre, element, element + 1);
                    swap(greatest, element, element + 1);
                    swap(recordLabel, element, element + 1);
                }//end if
            }//end for (int element = 0; element < tempArray.length - 1; element
        }//end for (int pass = 1; pass < tempArray.length; pass++)
        textPane = addTextToTextPane();//add the new text to the JTextPane

    }//end public void sort(String tempArray[])

    //method to swap two elements of an array
    public void swap(String swapArray[], int first, int second)
        String hold; //temporary holding area for swap
        hold = swapArray[first];
        swapArray[first] = swapArray[second];
        swapArray[second] = hold;
    }//end public void swap(String swapArray[], int first, int second)

    //main method executes at run time
    public static void main(String args[])
        MyMusic f = new MyMusic();
        f.setSize(900, 375);
    }//end public static void main(String args[])


To compare Strings for equality you need to use String.equals not ==:

 > if (arg == "SortArtist")
 > {
 > sort(artist);
 > }

This needs to be:

     if (arg.equals("SortArtist")) {


Knute Johnson
email s/nospam/knute/

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