Display tree map in gui java

Question

Firstly I am completely new to Java so please can you explain things as simple as possible!

So I have a treemap, the keys are dates which point to strings.

I want to display this on screen but am not sure how to do so.

I did come across JTable. After reasearching this I was confused as my columns were a string array (simply the titles of the two columns) whilst my data was a tree map. After looking further online I found I should create a table model but after reading through this I didn't really understand what I needed to do. Any help would be very much appreciated!

Thanks in advance.

Answer 1

The way you want to display your content varies depending on your requirement or on how the information could be displayed in an user-friendly way.

JTable is a good approach, JTree also is a good approach, although, I see JTable as a more standard way to do it.

I came with an approach I implemented really fast trying to simplify all the complex stuff and to fulfill what I understood from your question:

public class TableExample {

//Asuming you have a treemap like this
static Map<Date, String> sampleMap = new TreeMap<Date, String>();

//Initialize the sample treemap with some values (this static block will execute the first time we run this app)
static {
    sampleMap.put(createBirthdayFromString("14/02/1990"), "Marcelo's Birthday");
    sampleMap.put(createBirthdayFromString("29/06/1989"), "Oscar's Birthday");
    sampleMap.put(createBirthdayFromString("21/04/1985"), "Carlos' Birthday");
}

//This will create a date object based on a given String
public static Date createBirthdayFromString(String dateAsString) {
    SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
    Date convertedDate = null;
    try {
        convertedDate = formatter.parse(dateAsString);
    } catch (ParseException e) {
        // Print stacktrace and default to current Date
        e.printStackTrace();
        convertedDate = new Date();
    }
    return convertedDate;
}

public void init() {
    //Create the JFrame to display the table
    JFrame mainFrame = new JFrame();
    mainFrame.setTitle("My Table Example");
    mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    mainFrame.setSize(520, 520);

    //Then a panel to keep our Main frame available to display other contents
    JPanel myPanel = new JPanel();
    myPanel.setBounds(mainFrame.getBounds());
    myPanel.setBackground(Color.DARK_GRAY);
    myPanel.setVisible(true);

    //Add the panel to the frame
    mainFrame.add(myPanel);

    //You will need to specify the columns you want to display in your table, for this case:
    String[] columns = new String[] {"Birthday", "Name"};

    //Then you can create a table model with zero rows at the beginning
    //The table model will define how the data in your table would be displayed
    //As well as provide some useful methods if you want to add certain events or edition capabilities :)
    DefaultTableModel defaultModel = new DefaultTableModel(columns, 0);

    //Then you create your table based on your model
    JTable myTable = new JTable(defaultModel);

    //Then you will like to fill each table row with the data of your treemap

    //We iterate over your map to obtain the records
    for (Map.Entry<Date, String> entry : sampleMap.entrySet()) {
        defaultModel.addRow(new Object[] {entry.getKey(), entry.getValue()});
    }

    //Now add the table to your frame
    myPanel.add(new JScrollPane(myTable));

    //Set the frame visible
    mainFrame.setVisible(true);
}

/**
 * Main method that will execute this example
 * @param args
 */
public static void main(String[] args) {
    new TableExample().init();
}   
}

Please let me know if this helps you or you have any doubt. Happy coding! :)

Answer 2

A table model is responsible for managing the data that a JTable displays.

Entries in a JTable are referred to by row and column indexes, but a TreeMap does not have this kind of arrangement. We can still refer to entries in a TreeMap as if they were indexed, by iterating the entry set with a counter.

This is similar to, for example, iterating a linked list to retrieve an element by index.

To do the bare minimum, AbstractTableModel only requires that getRowCount, getColumnCount and getValueAt are implemented.

If you need the model to be editable, then implementing it gets more complicated.

class TreeMapTableModel extends AbstractTableModel {
    private TreeMap<?, ?> data;

    TreeMapTableModel(TreeMap<?, ?> data) {
        this.data = data;
    }

    private Map.Entry<?, ?> getEntryFor(int row) {
        int index = 0;
        for( Map.Entry<?, ?> entry : data.entrySet() ) {
            if( index == row )
                return entry;
            index++;
        }
        throw outOfBounds("row", row);
    }

    @Override
    public Object getValueAt(int row, int column) {
        Map.Entry<?, ?> entry = getEntryFor( row );

        switch( column ) {
            case 0: return entry.getKey();
            case 1: return entry.getValue();

            default: throw outOfBounds("column", column);
        }
    }

    @Override
    public int getRowCount() {
        return data.size();
    }

    @Override
    public int getColumnCount() {
        return 2;
    }

    private static IndexOutOfBoundsException outOfBounds(
            String parameter, int value) {
        return new IndexOutOfBoundsException(
            parameter + "=" + value);
    }
}