Question

I only studied till methods and am not patient enough to wait till my UNI teaches me the rest so i found this interesting… I want to create a GUI with a circle in the middle that moves according to what button you press with java. after alot of reading i managed to get it done this way. So before i got to the error mentioned in the question i had 19 errors and only when i figured all of them out this error suddenly appeared. I hope i don’t tick anybody’s nerve cause am sure this mistake is due to some lack of programming foundation.
any help will be very much appreciated. I pointed out where the error occured by “<—”

import java.awt.*;
import java.awt.event.*;
public class Move_the_ball extends Frame {

public static void main(String[] args) {
    Move_the_ball me = new Move_the_ball();
    me.setVisible(true);
}
public Move_the_ball(){
    setSize(700,700);
    setLocation(100,100);
    setTitle("Moving the ball");
    setLayout(new BorderLayout());
    Panel buttonPanel = new Panel();
    buttonPanel.setBackground(Color.blue);
    buttonPanel.setLayout(new FlowLayout());

    Button goUp = new Button("Go up");
    goUp.addActionListener(this); <-----------------
    buttonPanel.add(goUp);

    Button goDown = new Button("Go down");
    goDown.addActionListener(this); <--------------
    buttonPanel.add(goDown);


    Button turnRight = new Button("Turn right");
    turnRight.addActionListener(this);  <-------------
    buttonPanel.add(turnRight);


    Button turnLeft = new Button("Turn left");
    turnLeft.addActionListener(this); <---------------
    buttonPanel.add(turnLeft);
}
    public void paint(Graphics g)
        {
        g.fillOval(x,y,h,d);
}
    private int x=200;
    private int y=100;
    private int h=50;
    private int d=50;

    public void actionPerformed (ActionEvent e){
        String actionCommand = e.getActionCommand();
        if(actionCommand.equals("Go up"))
        {
            y=y-5;
            repaint();
        } else if (actionCommand.equals("Go down"))
        {
            y=y+5;
            repaint();
        } else if (actionCommand.equals("Turn right"))
        {
            x=x+5;
            repaint();
        } else if (actionCommand.equals("Turn left"));
        {
            x=x-5;
            repaint();
        }
    } 
 }

Answer 1

Your Move_the_ball class must implement java.awt.event.ActionListener interface for this to work.

import java.awt.*;
import java.awt.event.*;
public class Move_the_ball extends Frame implements ActionListener {

   public void actionPerformed(ActionEvent e) {
      // handle the e event
   }