2 (presumably) easy noob questions

Question

1.) I'm trying to implement actions for multiple buttons, but I'm struggling. Is it possible to do this within the same actionPerformed() method, or do I need one for each button? If I need one for each button, how would I set it up?
2.) Also, I'm trying to write to a file when I use the "OK" button, but it won't let me throw IOException in the actionPerformed() method. Is there any way to get around this, or can I not use a JButton action to write to a file?
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.io.*;
import java.util.*;
public class FlawTesterGUI extends JPanel implements ActionListener {
     // class constants
     private static final int WINDOW_WIDTH = 1500; // pixels
     private static final int WINDOW_HEIGHT = 1000; // pixels
     // window for GUI
     private JFrame window = new JFrame();
     private static final String INPUT_DEPTH = " Input Flaw Depth";
     private static final String INPUT_LENGTH = " Input Flaw Length";
     private static final String DIAMETER = " Select Line Diameter";
     private JLabel inputDepth = new JLabel(" Input Flaw Depth");
     private JLabel inputLength = new JLabel(" Input Flaw Length");
     // instance variables
     // legend
     private JTextArea depth = new JTextArea(INPUT_DEPTH, 1, 16);
     private JTextArea length = new JTextArea(INPUT_LENGTH, 1, 17);
     private JTextArea diameter = new JTextArea(DIAMETER, 1, 20);
     // user entry buttons for diameter
     private JButton dia1 = new JButton("1/4 in. (click once)");
     private JButton dia2 = new JButton("3/8 in. (click once)");
     private JButton dia3 = new JButton("1/2 in. (click once)");
     private JButton dia4 = new JButton("5/8 in. (click once)");
     private JButton dia5 = new JButton("3/4 in. (click once)");
     // user entry area for flaw depth and flaw length
     private JLabel mm = new JLabel("mm");
     private JTextField flawDepthText = new JTextField(10);
     private JTextField flawLengthText = new JTextField(10);
     // run button
     private JButton runButton = new JButton("OK");
     // output
     private JLabel theFlawIs = new JLabel(" The Flaw is ");
     private JTextField resultText = new JTextField(6);
     // FlawTesterGUI(): constructor
     public FlawTesterGUI() {
          // configure GUI
          window.setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
          depth.setEditable(false);
          depth.setLineWrap(true);
          depth.setWrapStyleWord(true);
          depth.setBackground(window.getBackground());
          depth.setFont(new Font("Dialog", Font.BOLD, 24));
          length.setEditable(false);
          length.setLineWrap(true);
          length.setWrapStyleWord(true);
          length.setBackground(window.getBackground());
          length.setFont(new Font("Dialog", Font.BOLD, 24));
          diameter.setEditable(false);
          diameter.setLineWrap(true);
          diameter.setWrapStyleWord(true);
          diameter.setBackground(window.getBackground());
          diameter.setFont(new Font("Dialog", Font.BOLD, 24));
          resultText.setEditable(false);
          resultText.setBackground(new Color(100,200,200));
          // implement ActionListeners
          runButton.addActionListener(this);     
          dia1.addActionListener(this);
          dia2.addActionListener(this);
          dia3.addActionListener(this);
          dia4.addActionListener(this);
          dia5.addActionListener(this);     
          // arrange components in GUI
          window.setLayout(new GridLayout(7, 5, 20, 20));
          // row 1
          window.add(diameter);
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          // row 2
          window.add(dia1);
          window.add(dia2);
          window.add(dia3);
          window.add(dia4);
          window.add(dia5);
          // row 3
          window.add(inputDepth);
          window.add(flawDepthText);
          window.add(new JLabel("mm"));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          // row 4
          window.add(inputLength);
          window.add(flawLengthText);
          window.add(new JLabel("mm"));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          // row 5
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          window.add(runButton);
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          // row 6
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          // row 7
          window.add(new JLabel(""));
          window.add(theFlawIs);
          window.add(resultText);
          window.add(new JLabel(""));
          window.add(new JLabel(""));
          // display GUI
          window.setVisible(true);
          // enable buttons
          dia1.setEnabled(true);
          dia2.setEnabled(true);
          dia3.setEnabled(true);
          dia4.setEnabled(true);
          dia5.setEnabled(true);
          runButton.setEnabled(true);
     public void actionPerformed(ActionEvent e) {
          String command = e.getActionCommand();
          String response1 = flawDepthText.getText();
          String response2 = flawLengthText.getText();
          if (command.equals("OK")) {
               /* this is the code I want:
               *File input = new File("input.txt");
               *FileWriter inputWriter = new FileWriter(input);
               *inputWriter.write(response1);
               *inputWriter.write(response2);
     // main(): application entry point
     public static void main(String[] args) throws IOException {
          FlawTesterGUI foobar = new FlawTesterGUI();
}

Answer 1

Is it possible to do this within the same actionPerformed() method, Yes, but it's not the best approach since you need to use a bunch of nested if/else statements
or do I need one for each button?This is the preferred approach.
One way to do this is to use Actions. Read this section from the Swing tutorial on "How to Use Actions" for more information:
http://java.sun.com/docs/books/tutorial/uiswing/misc/action.html
Another way to do this to create Anonymous Inner classes for each button:
JButton doSomething = new JButton("Do Somethingt");
doSomething.addActionListener( new ActionListener()
     public void actionPerformed(ActionEvent e)
          System.out.println("I'm doing something");
});Or simply create another class that implement the ActionListener interface. One class for each button.