How to restrict input to textboxes?

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Hello everyone. I am getting data via textbox but I want to restrict it. Namely, User can not enter character string or anything. I just want numeric characters between 100 and 999. Is it possible ?

String  coursecode = Integer.parseInt(txtCourseCode.getText());
if(coursecode<100 || coursecode>999)
           {
               JOptionPane.showMessageDialog(null,"Incorrect Course Code");
           }

this is a little part of my code.

Thanx.

Posted 30-Jul-12 3:21am

FoxRoot

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TorstenH. · Answer 1 · 2012-07-30T04:23:00

Validation is the keyword.

No matter if you create your own or use a mechanism that is provided, you just need to validate before you move on:

Java

public class CustomVerifier extends InputVerifier {
    @Override
    public boolean verify(JComponent input) {
    String text = ((JTextField) input).getText();
    // verify
     return true; // if ok
    // return false; // when not ok   
    }
}

and add to the JTextfield:

Java

oTextField.setInputVerifier(new CustomVerifier());

You can also use a listener (propertyChange, focus) and validate there.

EDIT:
Do I need to mention that you need to make a custom JDialog for this? I guess not. Have fun.

EDIT 2:

Version 1 with a Listener:

Java

  textField.addKeyListener(new KeyAdapter() { 
  // Adapter is a "small version of a Listener", 
  // which does implement just the   needed functions
  @Override
  public void keyReleased(KeyEvent oEvent) { 
  // disgard the Event, we just need it to have a chance to react.
    String strContent = textField.getText();
    try { 
      int i = Integer.parseInt(strContent); // check by simple parsing
      if(i<=0 || i>=1000) { // number between 1 and 
        JOptionPane.showMessageDialog(null, "This number is <1 or   >999.");
      }
      // everything is ok
    } catch (NumberFormatException oException) {
      JOptionPane.showMessageDialog(null,"This is not even a number.");
    }
});
  }
}

Version2 with InputVerifyer:

Java

textField.setInputVerifier(new InputVerifier() {
  @Override
  public boolean verify(JComponent input) {
    String strContent = textField.getText();
    try { 
      int i = Integer.parseInt(strContent); // check by simple parsing
      if(i<=0 || i>=1000) { // number between 1 and 
        JOptionPane.showMessageDialog(null, "This number is <1 or >999.");
      }
      // everything is ok
    } catch (NumberFormatException oException) {
      JOptionPane.showMessageDialog(null, "This is not even a number.");
    }
    return true;
  }
});

I hope Edit2 helps. You need to learn that!
Please buy a book to get such information without knowing the keywords.

I.explore.code · Answer 2 · 2012-07-30T03:44:00

Solution 1

Think this does count as a solution. You can try using Regular Expressions to restrict the input to numbers only and once that's done you can have a bounds check on the values, which you already have done in your code apparently.

Posted 30-Jul-12 3:44am

I.explore.code

Comments

FoxRoot 30-Jul-12 9:48am

Thanx for your comment. Isn't there any class or method to do that ?

I.explore.code 30-Jul-12 9:54am

i can't recall off the top of my head, its been a while since I last touched Java. But you can write your own which is basically doing an Integer.parseInt(string) in try block and if it succeeds, return true otherwise from the catch block return false. Something like this: http://stackoverflow.com/questions/1102891/how-to-check-a-string-is-a-numeric-type-in-java. Other approach is always Regular Expressions.

FoxRoot 31-Jul-12 2:10am

Thanx gladiatron.