private void popUp()
{
    JFrame frame = new JFrame("aName");
    frame.setSize(500, 500);
    frame.setVisible(true);
}

public void actionPerformed(ActionEvent event)
{
	if (event.getSource() == button1)	
                {
                        popUp();
                 }
}

button1.addActionListener(this);

 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import java.text.DecimalFormat;
import java.io.*;
import javax.swing.JOptionPane;
import java.math.*;
 
public class last_try implements ActionListener 
{
    // put variable declarations here (i.e. code below)
    JFrame f;
    JButton button1;
    JButton button2;
    // etc. for other variables
 
 
    public last_try()   // new constructor.  No longer have "static" limitiations
    {
        // code here that uses the variables declared above
        // see code below
 
 
        f = new JFrame("What would you like to do");
        f.setSize(400, 150);
        // more code to set up GUI
 
        button1 = new JButton("Button 1");
        button2 = new JButton("Button 2");
        button3 = new JButton("Button 3");
 
        button1.addActionListener(this);  // add action listeners here
        button2.addActionListener(this);
 
        // more code
 
 
        // need more code to use the line below, so commented out.
        // Are you sure you really want it?
        // f.addWindowListener(new ExitListener());
 
        f.setVisible(true);
    }
 
    public static void main(String[] args) 
    {
        last_try last = new last_try();
    }
 
    public void popUp() 
    {
        JFrame frame = new JFrame("aName");
        frame.setSize(500, 500);
        frame.setVisible(true);
    }
 
    public void actionPerformed(ActionEvent event) 
    {
        System.out.println("In actionPerformed");
 
        if (event.getSource() == button1)   // no quotes here
        {
            JOptionPane.showMessageDialog(null, "Your entry was not in the proper format.");
        }
    }
}