Restrict the Text in TextFeild

[Neha]

Hi,

Could u tell me a way,where I can restrict the characters to be typed to
4 only in a JTextfield.

I've used the constructor :
JTextField(int columns),but its not working.

Neha.

[MarkN]

You will have to create your own class(Subclass of JTextField) or buy a third
party widget.

Search the JTextField Class code for "insertString in the class comment section.

Mark


"Neha" <cool_sherll@yahoo.com> wrote:
>
>Hi,
>
>Could u tell me a way,where I can restrict the characters to be typed to
>4 only in a JTextfield.
>
>I've used the constructor :
>JTextField(int columns),but its not working.
>
>Neha.

[Ruchi Dhar]

Hi Neha

Subclass PlainDocument and override the insertString method. Use the following
example

import javax.swing.*;
import javax.swing.text.*;

import java.awt.*;

public class Test extends JFrame
{
public Test()
{
JTextField field1 = new JTextField(new LimitDocument(4), "", 20);
JPanel p = new JPanel();
p.add(field1);
getContentPane().add(p, BorderLayout.NORTH);
}

public static void main(String[] args)
{
Test t = new Test();
t.setSize(400, 400);
t.setVisible(true);
}
}

class LimitDocument extends PlainDocument
{
int maxLen;
public LimitDocument(int maxLen)
{
this.maxLen = maxLen;
}

public void insertString(int offs, String str, AttributeSet a) throws BadLocationException
{
if(getLength() >= this.maxLen)
{
Toolkit.getDefaultToolkit().beep();
} else
{
super.insertString(offs, str, a);
}
}
}


"Neha" <cool_sherll@yahoo.com> wrote:
>
>Hi,
>
>Could u tell me a way,where I can restrict the characters to be typed to
>4 only in a JTextfield.
>
>I've used the constructor :
>JTextField(int columns),but its not working.
>
>Neha.