Restricting a Java Text field to just a range of integers

Friday, April 11, 2014 java 0 Comments

This time I came across a slightly different way than extending the documentfilter. That is I will write my own plain document here.

class IntegerRangeDocument extends PlainDocument {

  int minimum, maximum;

  int currentValue = 0;

  public IntegerRangeDocument(int minimum, int maximum) {
    this.minimum = minimum;
    this.maximum = maximum;
  }

  public int getValue() {
    return currentValue;
  }

  public void insertString(int offset, String string, AttributeSet attributes)
      throws BadLocationException {

    if (string == null) {
      return;
    } else {
      String newValue;
      int length = getLength();
      if (length == 0) {
        newValue = string;
      } else {
        String currentContent = getText(0, length);
        StringBuffer currentBuffer = new StringBuffer(currentContent);
        currentBuffer.insert(offset, string);
        newValue = currentBuffer.toString();
      }
      try {
        currentValue = checkInput(newValue);
        super.insertString(offset, string, attributes);
      } catch (Exception exception) {
        Toolkit.getDefaultToolkit().beep();
      }
    }
  }

  public void remove(int offset, int length) throws BadLocationException {
    int currentLength = getLength();
    String currentContent = getText(0, currentLength);
    String before = currentContent.substring(0, offset);
    String after = currentContent.substring(length + offset, currentLength);
    String newValue = before + after;
    try {
      currentValue = checkInput(newValue);
      super.remove(offset, length);
    } catch (Exception exception) {
      Toolkit.getDefaultToolkit().beep();
    }
  }

  public int checkInput(String proposedValue) throws NumberFormatException {
    int newValue = 0;
    if (proposedValue.length() > 0) {
      newValue = Integer.parseInt(proposedValue);
    }
    if ((minimum <= newValue) && (newValue <= maximum)) {
      return newValue;
    } else {
      throw new NumberFormatException();
    }
  }
}

Now you can attach your text field with this plain document as below to achieve our requirement.

Document rangeOne = new IntegerRangeDocument(0, 255);
JTextField textFieldOne = new JTextField();
textFieldOne.setDocument(rangeOne);