Program For Weight Conversion GUI

I'm working on a Weight Conversion program. The code I have for the program is:

import java.util.*;
import java.awt.*;
import javax.swing.*;
public class Frame4a implements ActionListener {
public static void main(String[] args) {
JFrame f = new JFrame("Weight converter");
JPanel P = new JPanel(); // Make a JPanel;

[Code] .....

The errors I'm getting are:

Frame4a.java:33: error: class, interface, or enum expected
public void actionPerformed(ActionEvent e){
^
Frame4a.java:37: error: class, interface, or enum expected
double kp= Double.parseDouble(strkilo);

[Code] .....