Java 1.0 Applet -- Incompatible Types: Choice cannot be converted to Button -- Java In A Nutshell Example 1-2

Question

I am trying to compile example 1-2 from the Java In A Nutshell Book that deals with Java 1.0. I get an error saying that choice cannot be converted to Button. Now, I don't know whether this is an issue of current Java not supporting the libraries that I am calling, or the something is off.

The applet is supposed to be a sort of drawing pad, and the error is at line 14 / clear_button = new Choice();

import java.applet.*;
import java.awt.*;

public class Scribble extends Applet {
    private int last_x = 0;
    private int last_y = 0;
    private Color current_color = Color.black;
    private Button clear_button;
    private Choice color_choices;

public void init(){
    this.setBackground(Color.white);

    clear_button = new Choice();
    clear_button.setForeground(Color.black);
    clear_button.setBackground(Color.lightGray);
    this.add(clear_button);

    color_choices = new Choice();
    color_choices.addItem("black");
    color_choices.addItem("red");
    color_choices.addItem("yellow");
    color_choices.addItem("green");
    color_choices.setForeground(Color.black);
    color_choices.setBackground(Color.lightGray);
    this.add(new Label("Color: "));
    this.add(color_choices);
}

public boolean mouseDown(Event e, int x, int y){
    last_x = x; last_y = y;
    return true;
}

public boolean mouseDrag(Event e, int x, int y){
    Graphics g = this.setGraphics();
    g.setColor(current_color);
    g.drawline(last_x, last_y, x, y);
    last_x = x;
    last_y = y;
    return true;
}

public boolean action(Event event, Object arg) {
    if (event.target == clear_button) {
        Graphics g = this.getGraphics();
        Rectangle r = this.bounds();
        g.setColor(this.getBackground());
        g.fillRect(r.x, r.y, r.width, r.height);
        return true;
    }

    else if (event.target == color.choices) {
        if (arg.equals("black")) current_color = color.black;
        else if (arg.equals("red")) current_color = color.red;
        else if (arg.equals("yellow")) current_color = color.yellow;
        else if (arg.equals("green")) current_color = color.green;
        return true;
    }

    else return super.action(event, arg);

 }
}

Answer 1

This is because Choice does not extend from Button. The type is incompatible.

https://docs.oracle.com/javase/7/docs/api/java/awt/Choice.html

In order to fix this you need to change the type of clear_button to Choice like this:

private Choice clear_button;

I just checked the old java 1.0.2 documentation and there Choice is also not extending from Button:

http://web.mit.edu/java_v1.0.2/www/javadoc/java.awt.Choice.html#top

Based on your comment this.setGraphics() does not exist neither in Java 1.0.2 neither in modern Java.

Judging from your code you should replace it with this.getGraphics().

Another way to obtain a handler to Graphics would be to override the:

public void paint(Graphics g)

You can override this method in your class.