Question

How can I actually use delimeter in java, this is the example data.dat file

   1 yuri
   2 fisher
   3 McMillan
   4 price
   5 soap

how can I only get the first numbers in every lines in the file and using useDelimiter() method

how can I do that to this code

Scanner src = new Scanner(fin);
                                 src.useDelimiter(" \n");
                                DefaultListModel model = new DefaultListModel();
                                while (src.hasNext()) {
                                String lol = src.nextLine();
                                model.addElement(lol);
                                }
                                list.setModel(model);
                                } 
                                });

This is the whole code.. Uhmm.. It’s not always ‘lol’ in the file I’ll change It later

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.DefaultListModel;
import javax.swing.DefaultListSelectionModel;
import javax.swing.ListSelectionModel;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Jfetizanan
 */
@SuppressWarnings("serial")
public class IOtestForm extends javax.swing.JFrame {

    /**
     * Creates new form IOtest
     */
    public IOtestForm() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        list = new javax.swing.JList();
        input0 = new javax.swing.JTextField();
        load = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jScrollPane1.setViewportView(list);
        DefaultListSelectionModel m = new DefaultListSelectionModel();
        m.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        m.setLeadAnchorNotificationEnabled(false);
        list.setSelectionModel(m);
        list.addListSelectionListener(new ListSelectionListener() {
            @Override
        public void valueChanged(ListSelectionEvent e) {
        int selected[] = list.getSelectedIndices();
        for (int i = 0; i < selected.length; i++) {
        String element = (String) list.getModel().getElementAt(selected[i]);
        input0.setText(element);
        }}});

        load.setText("Load");
        load.addActionListener(new ActionListener() {
                            @Override
            @SuppressWarnings("unchecked")
                            public void actionPerformed(ActionEvent e) {
                                 FileReader fin = null;
                            try {
                                 fin = new FileReader("data.dat");
                                } catch (FileNotFoundException ex) {
                                   Logger.getLogger(IOtestForm.class.getName()).log(Level.SEVERE, null, ex);
                                }
                                Scanner src = new Scanner(fin);
                                src.useDelimiter("\\s*lol\\s*");
                                DefaultListModel model = new DefaultListModel();
                                while (src.hasNext()) {
                                String lol = src.next();
                                model.addElement(lol);
                                }
                                list.setModel(model);
                                } 
                                });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 380, Short.MAX_VALUE)
                    .addComponent(input0)
                    .addComponent(load, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(13, 13, 13)
                .addComponent(load)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(input0, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(94, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(IOtestForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }

        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new IOtestForm().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JTextField input0;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JList list;
    private javax.swing.JButton load;
    // End of variables declaration
}

Answer 1

Let’s start with the basic

To load the file, you would do this

Scanner src = new Scanner(is);
while (src.hasNext()) {

    int line = src.nextInt();
    String value = src.next();

    System.out.println(line + " = " + value);

}

Now, what we really need is some way to model this information. A better solution would be to create a Object of some kind that represents this information that makes it easier to manage.

Something like

public class LineOfText {

    private int line;
    private String value;

    public LineOfText(int line, String value) {
        this.line = line;
        this.value = value;
    }

    public int getLine() {
        return line;
    }

    public String getValue() {
        return value;
    }

}

Okay, then we need to apply the properties from the file to it.

Scanner src = new Scanner(is);
while (src.hasNext()) {

    int line = src.nextInt();
    String value = src.next();

    LineOfText lot = new LineOfText(line, value);

}

This we can add to the ListModel you’ve already created.

model.addElement(lot);

Now if we display this on our UI, it doesn’t look very pretty. What we really need is some way to “render” the text more efficiently.

Something like

public class LineOfTextListCellRenderer extends DefaultListCellRenderer {

    @Override
    public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {

        if (value instanceof LineOfText) {

            value = ((LineOfText)value).getLine();

        }

        return super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);

    }

}

Should do. We need to apply this renderer to the list you created earlier.

list.setListCellRenderer(new LineOfTextListCellRenderer());

Now, if we display this on the UI, we should only see the line numbers in the list.

Next, we need some way to detect the change of selection. For this we need a ListSelectionListener

list.addListSelectionListener(new ListSelectionListener() {

    @Override
    public void valueChanged(ListSelectionEvent e) {

        Object item = list.getSelectedItem();
        if (item != null && item instance of LineOfText) {
            ListOfText lot = (LineOfText)lot;
            // Now we have access to the text value
            // Simply use "setText" on the text area to apply it

            textArea.setText(lot.getValue());

            // Remember, "textArea" should be replaced with the name
            // of your text area
        }

    }

});

Now you see why it was a separate question 😉