How to round a JSpinner value to 2 decimals?

Question

I am currently trying to create a JSpinner that only accepts monetary values, i.e. a maximum of 2 decimals, and I tried to accomplish this using this code:

priceSpinner = new JSpinner();
SpinnerNumberModel priceSpinnerModel = new SpinnerNumberModel(
        Double.valueOf(0d), 
        Double.valueOf(0d), 
        null, 
        Double.valueOf(0.01d));
priceSpinner.setModel(priceSpinnerModel);
priceSpinner.setEditor(new JSpinner.NumberEditor(priceSpinner, "0.00"));

However, when I input a number that contains more than 2 decimals, the spinner rounds it off to 3 decimals instead. What am I doing wrong?

Answer 1

Works fine for me. I cannot reproduce your problem. Consider the below code.

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JButton;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSpinner;
import javax.swing.SpinnerNumberModel;

public class SpinTest {

    private void createAndDisplayGui() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(createSpinner(), BorderLayout.PAGE_START);
        frame.add(createButtons(), BorderLayout.PAGE_END);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createButtons() {
        JPanel panel = new JPanel();
        JButton button = new JButton("Exit");
        button.addActionListener(e -> System.exit(0));
        panel.add(button);
        return panel;
    }

    private JPanel createSpinner() {
        JPanel panel = new JPanel();
        SpinnerNumberModel priceSpinnerModel = new SpinnerNumberModel(0d, 0d, null, 0.01d);
        JSpinner priceSpinner = new JSpinner(priceSpinnerModel);
        JSpinner.NumberEditor editor = new JSpinner.NumberEditor(priceSpinner, "#,##0.00");
        JFormattedTextField textField = editor.getTextField();
        textField.setColumns(12);
        priceSpinner.setEditor(editor);
        panel.add(priceSpinner);
        return panel;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> new SpinTest().createAndDisplayGui());
    }
}

If I enter a number with more than two digits after the decimal point, it gets rounded to precisely two digits.

Refer to How to Use Spinners and javadoc for class java.text.DecimalFormat