Java Swing JTextField: Number only and give length

Solution 1

Simple but It can't work for "CTRL + V" scenario

private class NumberOnlyAdapter extends KeyAdapter {

        private final int maxLength;

        private NumberOnlyAdapter(int maxLength) {
            this.maxLength = maxLength;
        }

        @Override
        public void keyTyped(KeyEvent e) {
            char typed = e.getKeyChar();
            CharMatcher notDigit = noneOf("0123456789").and(isNot((char) VK_BACK_SPACE)).and(isNot((char) VK_DELETE));
            JTextField textField = (JTextField) e.getComponent();
            if (notDigit.apply(typed) || textField.getText().length() >= maxLength) {
                e.consume();
            }
        }

    }

...
int maxLength = 8;
JTextField textField = new JTextField();
textField.addKeyListener(new NumberOnlyAdapter(maxLength));

Solution 2

It's work for all conditions

import static org.apache.commons.lang3.StringUtils.*;

import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;

public class NumericOnlyAndMaxLengthFilter extends DocumentFilter {
    private int maxLength = 0;


    public NumericOnlyAndMaxLengthFilter() {
       // allow any length of numeric
    }

    public NumericOnlyAndMaxLengthFilter(int maxLength) {
        this.maxLength = maxLength;
    }

    @Override
    public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
        if (isNumeric(string)) {
            if (isExceedMaxLength(fb, string)) {
                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 (isExceedMaxLength(fb, text)) {
                return;
            }
            super.insertString(fb, offset, text, attrs);
        }
    }

    private boolean isExceedMaxLength(FilterBypass fb, String text) {
        return maxLength > 0 && (fb.getDocument().getLength() + text.length()) > maxLength;
    }
}

...
int maxLength = 8;
JTextField textField = new JTextField();
((AbstractDocument)textField .getDocument()).setDocumentFilter(new NumericOnlyAndMaxLengthFilter(maxLength));