Jtextfield Validation

**nimishalex** · December 9th, 2010, 04:15 AM

Hi all

In my Swing application i am using Jtextfields.If Jtextfield have empty string("") i need to set it to 0 always .Is there any easy way to set this without if else comparison.

Thanks

Nimish

**relixus** · December 9th, 2010, 04:20 AM

Why dont you try JFormattedTextField instead?

**nimishalex** · December 9th, 2010, 04:42 AM

hi relixus
i am newbie here. Can u give me some example how to use JFormattedTextfield for this.

Thanks

**JavaPF** · December 9th, 2010, 09:07 AM

Why can't you use if/else?

Just to clarify, if the text is deleted out of the textfield, you want it to automatically update to 0?

**nimishalex** · December 10th, 2010, 02:24 AM

Hello PF
Really thats i want .. I want to automatically updated into 0.

Thanks

**JavaPF** · December 10th, 2010, 07:52 AM

Does this need to check in real-time? When the user is typing/deleting text from the field or does it check when a button is pressed?

**nimishalex** · December 10th, 2010, 08:05 AM

Hi PF

i need to check in when the user is typing/deleting. Plz help me to find a solution ,,Thanks

**JavaPF** · December 10th, 2010, 09:09 AM

Have a play with this code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
 
public class TextValidation {
 
	/**
	 * JavaProgrammingForums.com
	 */	
	public static MyTextField t = new MyTextField(16);
 
	public static void main(String[] a) {
 
		JFrame f = new JFrame("JAVA FORUMS");
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		//MyTextField t = new MyTextField(16);
		t.setText("0");
		f.getContentPane().add(t, BorderLayout.CENTER);
		f.pack();
		f.setVisible(true);
	}
 
	private static class MyTextField extends JTextField implements
			ActionListener, DocumentListener {
 
		public MyTextField(int l) {
			super(l);
			addActionListener(this);
			Document doc = this.getDocument();
			doc.addDocumentListener(this);
		}
 
		//Enter key pressed
		public void actionPerformed(ActionEvent e) {
			//System.out.println(getText());
		}
 
		//Text inserted
		public void insertUpdate(DocumentEvent e) {
			//System.out.println(getText());
		}
 
		//Text deleted
		public void removeUpdate(DocumentEvent e) {
			//System.out.println(getText());
			if(getText().equals("")){
				System.out.println("IM BLANK!");
			}
		}
 
		public void changedUpdate(DocumentEvent e) {
			//System.out.println(getText());
		}
 
	}
}

**nimishalex** · December 11th, 2010, 02:42 AM

 public void removeUpdate(DocumentEvent e) {
            //System.out.println(getText());
            if(getText().equals("")){
              setText("0");
            }
        }

I tried the above .But i got Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Attempt to mutate in notification.I Google it. Using DoucmentFilter may slove the problem.

public class Doc extends DocumentFilter {
    public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException
    {
 
        super.insertString(fb, offset, string, attr);
    }
 
      public void remove(FilterBypass fb, int offset, int length) throws BadLocationException
    {
//    
 
        super.remove(fb, offset, length);
       if(fb.getDocument().getLength()==0)
       {
           insertString(fb, offset, "0", null);
 
       }
 
    }
    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException
    {
//      super.replace(fb, offset, length, text, attrs);
         if(fb.getDocument().getText(0, 1).equals("0"))
        {
            remove(fb, 0, 1);
        }
 
    }
}

But dont know it's the exact way of doing this .Plz let me know if u have any suggestions.

Thanks

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