Restrict a java text field length

Sunday, April 13, 2014 java 0 Comments

There are many different way to do this. You might write your own once you figure out what has to be done exactly. But I came up with this. Additionally I wanted the input to be numeric as well. So below is what I came up with.

private class NumericAndLengthFilter extends DocumentFilter {
 /**
 * Number of characters allowed.
 */
 private int length = 0;
 /**
 * Restricts the number of charcacters can be entered by given length.
 * @param length Number of characters allowed.
 */
 public NumericAndLengthFilter(int length) {
 this.length = length;
 }
 @Override
 public void insertString(FilterBypass fb, int offset, String string,
 AttributeSet attr) throws
 BadLocationException {
 if (isNumeric(string)) {
 if (this.length> 0 && fb.getDocument().getLength() + string.
 length()
> this.length) {
 return;
 }
 super.insertString(fb, offset, string, attr);
 }
 }
 @Override
 public void replace(FilterBypass fb, int offset, int length, String text,
 AttributeSet attrs) throws
 BadLocationException {
 if (isNumeric(text)) {
 if (this.length> 0 && fb.getDocument().getLength() + text.
 length()
> this.length) {
 return;
 }
 super.insertString(fb, offset, text, attrs);
 }
 }
 /**
 * This method tests whether given text can be represented as number.
 * This method can be enhanced further for specific needs.
 * @param text Input text.
 * @return {@code true} if given string can be converted to number; otherwise returns {@code false}.
 */
 private boolean isNumeric(String text) {
 if (text == null || text.trim().equals("")) {
 return false;
 }
 for (int iCount = 0; iCount < text.length(); iCount++) { if (!Character.isDigit(text.charAt(iCount))) { return false; } } return true; } } } 

Vijay