How would I create a subclass of jtextfield that restricts input to decimal numbers for this code? .

package lab5;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Calculator extends JFrame implements ActionListener {
 
private final Container con = getContentPane();
JLabel prompt = new JLabel("First Number");
JLabel prompt2 = new JLabel("Second Number");
JLabel result = new JLabel();
Font promptFont = new Font("Times", Font.BOLD, 12);
Font resultFont = new Font("Times", Font.BOLD, 20);

JTextField input = new JTextField(20);
JTextField input2 = new JTextField(20);

JButton add = new JButton("Add");
JButton subtract = new JButton("Subtract");
JButton multiply = new JButton("Multiply");
JButton divide = new JButton("Divide");

public Calculator(){
 
 super("CALCULATOR");
 setSize(300,300);
 con.setLayout(new FlowLayout());
 prompt.setFont(promptFont);
 prompt2.setFont(promptFont);
 result.setFont(resultFont);
 
 con.add(prompt);
 con.add(input);
 con.add(prompt2);
 con.add(input2);
 con.add(add);
 con.add(subtract);
 con.add(multiply);
 con.add(divide);
 con.add(result);

 add.addActionListener(this);
 subtract.addActionListener(this);
 multiply.addActionListener(this);
 divide.addActionListener(this);
   
} 
public static void main(String[] args){
 
 Calculator demo = new Calculator();
 demo.setVisible(true);
 
}

@Override
public void actionPerformed(ActionEvent e) {
 
 Object source = e.getSource();
 if(source == add)
 {
  String ans1 = input.getText();
  int num1 = Integer.parseInt(ans1);
  String ans2 = input2.getText();
  int num2 = Integer.parseInt(ans2); 
  
  int RESULT = num1 + num2;
  String res = Integer.toString(RESULT);
  result.setText("The result is" + res);       
 }
 
 if(source == subtract)
 {
  String ans1 = input.getText();
  int num1 = Integer.parseInt(ans1);
  String ans2 = input2.getText();
  int num2 = Integer.parseInt(ans2); 
  
  int RESULT = num1 - num2;
  String res = Integer.toString(RESULT);
  result.setText("The result is" + res); 
 }
 
 if(source == multiply)
 {
  String ans1 = input.getText();
  int num1 = Integer.parseInt(ans1);
  String ans2 = input2.getText();
  int num2 = Integer.parseInt(ans2); 
  
  int RESULT = num1 * num2;
  String res = Integer.toString(RESULT);
  result.setText("The result is" + res);
 }
 
 if(source == divide)
 {
  String ans1 = input.getText();
  double num1 = Double.parseDouble(ans1);
  String ans2 = input2.getText();
  double num2 = Double.parseDouble(ans2); 
  
  Double RESULT = num1 / num2;
  String res = RESULT.toString();
  result.setText("The result is" + res);  
 }
 
}

}

ExitValidator validator = new ExitValidator();
JTextField bla = bew JTextField(2);
bla.addFocusListener(validator);