用java图形界面实现输入两个数作为上限和下限，求区间内所有素数并显示出来

查找质数的算法就不用多说了，这里省略在注释中

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

public class PrimeGUI extends JFrame implements ActionListener
{
private JButton button;
private JTextArea area;
private JTextField field1, field2;

public PrimeGUI()
{
button = new JButton("Run");
area = new JTextArea(12,15);
field1 = new JTextField(4);
field2 = new JTextField(4);

button.addActionListener(this);

Container ct = getContentPane();
ct.setLayout(new FlowLayout());
ct.add(field1);
ct.add(field2);
ct.add(button);
ct.add(area);

setSize(200,300);
setVisible(true);
}

public void actionPerformed(ActionEvent e)
{
try
{
int a = Integer.parseInt(field1.getText());
int b = Integer.parseInt(field2.getText());
area.setText(calculatePrime(