How to validate jtextfield which accepts only float/decimal value in java swing?

Question

I am trying to validate text field such that it accepts float or double values like .25, 0.2, 111.25
It should not accepts values like ...25, 0.2.2. etc

Duplicate. http://stackoverflow.com/questions/9341695/regex-to-match-any-number-real-rational-along-with-signs — christopher, Apr 08 '13 at 09:51
The same as for numeric values (shown [here](http://stackoverflow.com/a/13424140/1076463)), but using another `java.text.Format` — Robin, Apr 08 '13 at 10:06
possible duplicate of [Is there any way to accept only numeric values in a JTextField?](http://stackoverflow.com/questions/1313390/is-there-any-way-to-accept-only-numeric-values-in-a-jtextfield) — Robin, Apr 08 '13 at 10:07
but for validation of form i am not getting it, using jtextfield only. — Chaitanya Gadam, Apr 08 '13 at 10:19

mKorbel · Answer 1 · 2013-04-08T10:18:32.850

use JFormattedTextField with Number Formatter
otherwise (for plain JTextField) you have to create an own DocumentFilter with InputMask and InputVerifier

JFormattedTextField example

enter image description here

import java.awt.*;
import java.awt.font.TextAttribute;
import java.math.*;
import java.text.*;
import java.util.Map;
import javax.swing.*;
import javax.swing.JFormattedTextField.*;
import javax.swing.event.*;
import javax.swing.text.InternationalFormatter;

public class DocumentListenerAdapter {

    public static void main(String args[]) {
        JFrame frame = new JFrame("AbstractTextField Test");
        final JFormattedTextField textField1 = new JFormattedTextField(new Float(10.01));
        textField1.setFormatterFactory(new AbstractFormatterFactory() {

            @Override
            public AbstractFormatter getFormatter(JFormattedTextField tf) {
                NumberFormat format = DecimalFormat.getInstance();
                format.setMinimumFractionDigits(2);
                format.setMaximumFractionDigits(2);
                format.setRoundingMode(RoundingMode.HALF_UP);
                InternationalFormatter formatter = new InternationalFormatter(format);
                formatter.setAllowsInvalid(false);
                formatter.setMinimum(0.0);
                formatter.setMaximum(1000.00);
                return formatter;
            }
        });
        final Map attributes = (new Font("Serif", Font.BOLD, 16)).getAttributes();
        attributes.put(TextAttribute.STRIKETHROUGH, TextAttribute.STRIKETHROUGH_ON);
        final JFormattedTextField textField2 = new JFormattedTextField(new Float(10.01));
        textField2.setFormatterFactory(new AbstractFormatterFactory() {

            @Override
            public AbstractFormatter getFormatter(JFormattedTextField tf) {
                NumberFormat format = DecimalFormat.getInstance();
                format.setMinimumFractionDigits(2);
                format.setMaximumFractionDigits(2);
                format.setRoundingMode(RoundingMode.HALF_UP);
                InternationalFormatter formatter = new InternationalFormatter(format);
                formatter.setAllowsInvalid(false);
                //formatter.setMinimum(0.0);
                //formatter.setMaximum(1000.00);
                return formatter;
            }
        });
        textField2.getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void changedUpdate(DocumentEvent documentEvent) {
                printIt(documentEvent);
            }

            @Override
            public void insertUpdate(DocumentEvent documentEvent) {
                printIt(documentEvent);
            }

            @Override
            public void removeUpdate(DocumentEvent documentEvent) {
                printIt(documentEvent);
            }

            private void printIt(DocumentEvent documentEvent) {
                DocumentEvent.EventType type = documentEvent.getType();
                double t1a1 = (((Number) textField2.getValue()).doubleValue());
                if (t1a1 > 1000) {
                    Runnable doRun = new Runnable() {

                        @Override
                        public void run() {
                            textField2.setFont(new Font(attributes));
                            textField2.setForeground(Color.red);
                        }
                    };
                    SwingUtilities.invokeLater(doRun);
                } else {
                    Runnable doRun = new Runnable() {

                        @Override
                        public void run() {
                            textField2.setFont(new Font("Serif", Font.BOLD, 16));
                            textField2.setForeground(Color.black);
                        }
                    };
                    SwingUtilities.invokeLater(doRun);
                }
            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(textField1, BorderLayout.NORTH);
        frame.add(textField2, BorderLayout.SOUTH);
        frame.setVisible(true);
        frame.pack();
    }

    private DocumentListenerAdapter() {
    }
}

how to create an own DocumentFilter with InputMask and InputVerifier for plain JTextField? — Chaitanya Gadam, Apr 08 '13 at 09:53
please whats wrong with JFormattedTextField with Number Formatter — mKorbel, Apr 08 '13 at 10:17

score 3 · Accepted Answer · answered Apr 08 '13 at 09:49

3

-?(\d*\.)?\d+([eE][+\-]?\d+)?|[nN]a[nN]|[iI]nf(inity)? is the regex I usually use for parsing doubles.

If you don't want infinities and NaNs,

-?(\d*\.)?\d+([eE][+\-]?\d+)?

If you also don't want exponential notation,

-?(\d*\.)?\d+

And don't forget to escape backslashes if you need to.

answered Apr 08 '13 at 09:49

Patashu

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@Chaitanya Gadam I am testing the regex in the python interpreter and it works fine for me. – Patashu Apr 08 '13 at 10:04
do you have any idea doing this in java swing? – Chaitanya Gadam Apr 08 '13 at 10:07
@Chaitanya Gadam Use a debugger. Is the string that matches is called on exactly what you expected? Simplify the problem. Write a test case that tries the regex on known strings. Does it work when you expect and not when you don't? Why or why not? – Patashu Apr 08 '13 at 10:08

score 3 · Answer 3 · answered May 21 '15 at 13:04

Create a class that extends PlainDocument and then set the jtextfield setDocument() to your new document class.

import java.awt.Toolkit;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

public class DoubleDocument extends PlainDocument {

    int size;

    public DoubleDocument(int size) {
        this.size = size;
    }

    @Override
    public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
        if(str == null){
            return;
        }

        if(getLength() + str.length() > size){
            Toolkit.getDefaultToolkit().beep();
            return;
        }

        boolean isValid = true;
        for(int i = 0; i < str.length(); i++){
            if(!Character.isDigit(str.charAt(i))){
                if(str.charAt(i) != '.'){
                    isValid = false;
                    break;
                } else {
                    if(this.getText(0, this.getLength()).contains(".")){
                        isValid = false;
                        break;
                    }
                }
            }
        }

        if(isValid){
            super.insertString(offs, str, a);
        } else {
            Toolkit.getDefaultToolkit().beep();
        }
    }

}

then implement like this.

txtLoanAmount.setDocument(new DoubleDocument(12));

you can choose to remove the size in the DoubleDocument class if you don't care about the length of the field. Hope this helps.

How to validate jtextfield which accepts only float/decimal value in java swing?

3 Answers3