So I've been working on a homework on abstraction for my programming class and fell into a problem. The goal for me right now is to be able to use abstraction, then later be able to draw with rectangles and ovals a simple city, like a rectangular building or a oval light on a light post.
The error I am receiving when I compile is: MyTestApp.Rectangle is not abstract and does not override abstract method drawEllipse(java.awt.Graphics) in MyTestApp.Shape. This Error shows up on the line "class Rectangle extends Shape{" right below the class Shape.
My question is what am I doing wrong with my abstraction? I've been messing with the constructors and draw() methods in classes Rectangle and Ellipse for a while now and still to no luck happen to find a solution.
Code is below:
import java.awt.*;
import javax.swing.*;
public class MyTestApp extends JPanel {
Rectangle rect;
Ellipse oval;
public static void main(String [] args) {
MyTestApp myTestApp = new MyTestApp ();
myTestApp.test();
}
public MyTestApp () { //creates the jframe
JFrame frame = new JFrame("MyClass Driver");
setBackground(new Color(200, 250, 200));
setPreferredSize(new Dimension(500, 400));
frame.add(this);
frame.pack();
frame.setVisible(true);
}
public void delay(int msecs) {
try {
Thread.sleep(msecs);
} catch (InterruptedException e) {
}
}
public void paint(Graphics g) {//paints the rectangle and ellipse
super.paint(g);
if (rect != null)
rect.drawRectangle(g);
if (oval != null)
oval.drawEllipse(g);
}
public void test() {//gives the x/y position, width/height, and fill/outline color for the rectangle and oval
delay(1000);
rect = new Rectangle(20, 30, 23, 75, Color.GREEN, Color.BLUE);
oval = new Ellipse(10, 10, 10 , 34, Color.RED, Color.MAGENTA);
repaint();
}
public abstract class Shape{//abstract class Shape that sets the x/y, width/height, and colors for the shapes
private int x, y, width, height;
private Color fillColor;
private Color outlineColor;
public Shape(int x, int y, int width, int height, Color fillColor, Color outlineColor) {
setXY(x, y);
setSize(width, height);
setFillColor(fillColor);
setOutlineColor(outlineColor);
}
public boolean setXY(int x, int y) {
this.x = x;
this.y = y;
return true;
}
public void setSize(int width, int height) {
if (width > 0)
this.width = width;
if (height > 0)
this.height = height;
}
public boolean setFillColor(Color fillColor){
if (fillColor == null) return false;
this.fillColor = fillColor;
return true;
}
public boolean setOutlineColor(Color outlineColor){
if (outlineColor == null) return false;
this.outlineColor = outlineColor;
return true;
}
public Color getFillColor() {
return fillColor;
}
public Color getOutlineColor() {
return outlineColor;
}
public abstract void drawRectangle(Graphics g);//do i need two?
public abstract void drawEllipse(Graphics g);//do i need both?
}
class Rectangle extends Shape{//!!!!!!!!!! where the error shows
public Rectangle(int x, int y, int width, int height, Color fillColor, Color outlineColor) {
super(x, y, width, height, fillColor, outlineColor);
}
public void drawRectangle(Graphics g){//draws the retangle
g.setColor(fillColor);
g.fillRect(x, y, width, height);
g.setColor(outlineColor);
g.drawRect(x, y, width, height);
}
}
class Ellipse extends Shape{
public Ellipse(int x, int y, int width, int height, Color fillColor, Color outlineColor) {
super(x, y, width, height, fillColor, outlineColor);
}
public void drawEllipse(Graphics g){//draws the ellipse
g.setColor(fillColor);
g.fillOval(x, y, width, height);
g.setColor(outlineColor);
g.drawOval(x, y, width, height);
}
}
}
Thanks for reading and helping!
Both classes Rectangle and Ellipse need to override both of the abstract methods.
To work around this, you have 3 options:
Have a single method that does the function of the classes that will extend Shape, and override that method in Rectangle and Ellipse, for example:
abstract class Shape {
// ...
void draw(Graphics g);
}
And
class Rectangle extends Shape {
void draw(Graphics g) {
// ...
}
}
Finally
class Ellipse extends Shape {
void draw(Graphics g) {
// ...
}
}
And you can switch in between them, like so:
Shape shape = new Ellipse();
shape.draw(/* ... */);
shape = new Rectangle();
shape.draw(/* ... */);
Again, just an example.
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