Make a JFormattedTextField behave like ATM input

Question

I would like to know if there is anyway to make a JformattedTextField or jtextField behave like an atm money input. With that I mean you enter from the right to left, say yo

Answer 1

Take a look at How to use Formatted Text Fields, in particular Using MaskFormatter.

Something like...

MaskFormatter formatter = new MaskFormatter("##.##");
JFormattedTextField field = JFormattedTextField(formatter);

for example may help.

Simple example

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.HeadlessException;
import java.text.ParseException;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.text.DefaultFormatterFactory;
import javax.swing.text.MaskFormatter;

public class TestFormattedTextField {

    public static void main(String[] args) {
        new TestFormattedTextField();
    }

    public TestFormattedTextField() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                try {
                    JFormattedTextField field = new JFormattedTextField();
                    MaskFormatter formatter = new MaskFormatter("##.##");
                    formatter.setPlaceholderCharacter('0');
                    field.setFormatterFactory(new DefaultFormatterFactory(formatter));

                    JFrame frame = new JFrame("Testing");
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setLayout(new GridBagLayout());
                    frame.add(field);
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (ParseException exp) {
                    exp.printStackTrace();
                }
            }
        });
    }        
}

Additional Example

Now, I realise that the previous example doesn't meet your exact needs (as you described them), it is a simple solution, I've also added a DocumentFilter example...

Which will output...

Value = 0.1
Value = $0.10

Which will output

Value = 10.0
Value = $10.00

Code...

import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.NumberFormat;
import java.text.ParseException;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import javax.swing.text.MaskFormatter;

public class TestFormattedTextField {

    public static void main(String[] args) {
        new TestFormattedTextField();
    }

    public TestFormattedTextField() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                MoneyField field = new MoneyField();
                field.addActionListener(new ActionListener() {
                    @Override
                    @SuppressWarnings("empty-statement")
                    public void actionPerformed(ActionEvent e) {
                        MoneyField field = (MoneyField) e.getSource();
                        double value = field.getValue();
                        System.out.println("Value = " + value);
                        System.out.println("Value = " + NumberFormat.getCurrencyInstance().format(value));
                    }
                });

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridBagLayout());
                frame.add(field);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class MoneyField extends JTextField {

        public MoneyField() {
            setColumns(5);
            setHorizontalAlignment(RIGHT);
            ((AbstractDocument) getDocument()).setDocumentFilter(new Filter());
        }

        public double getValue() {

            String text = getText();
            if (!text.contains(".")) {
                text = "0." + text;
            }

            return Double.parseDouble(text);

        }

        protected class Filter extends DocumentFilter {

            protected String getNumbers(String text) {
                StringBuilder sb = new StringBuilder(text.length());
                for (char c : text.toCharArray()) {
                    if (Character.isDigit(c)) {
                        sb.append(c);
                    }
                }
                return sb.toString();
            }

            @Override
            public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
                if (length > 0) {
                    fb.remove(offset, length);
                }
                insertString(fb, offset, text, attrs);
            }

            @Override
            public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
                text = getNumbers(text);
                if (text.length() > 0) {
                    int docLength = fb.getDocument().getLength();
                    if (docLength == 2) {
                        text = "." + text;
                    }
                    if (docLength + text.length() < 6) {
                        super.insertString(fb, offset, text, attr);
                    }
                }
            }

            @Override
            public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
                if (offset == 3) {
                    offset = 2;
                    length = 2;
                }
                super.remove(fb, offset, length);
            }
        }
    }
}

Check out DocumentFilter examples for more details