CODEWITHSUNDEEP
java
zurfyx
zurfyx

Reputation: 32767

Java - Passing object into extended class

Let's say I have two public classes like the ones below:

The oval class which will get the width and height parameters.

public class Oval extends Shape{
    OvalClass oval;
    public Oval(int width,int height){
        oval = new OvalClass("first",10);
    }

}

and a Shape class which is supposed to have any different form (that's why I'm extending it).

public class Shape {

    public void moveLeft(){
      //object?
      object.posX += 1;
  }
}

EDIT:

We don't know enough about GOval, the other classes, and the move() method to give a good answer.

Consider this other OvalClass as the oval class:

public class OvalClass {
    String name;
    int posX;
    public OvalClass(String name, int posx){}
}

The thing is, how can I get the object oval (GOval oval) created in the Oval in the Shape class? Is there any better approach?

Upvotes: 0

Views: 381

Answers (4)

Rainbolt
Rainbolt

Reputation: 3660

Moving left and right is not something that only ovals do, or only squares. Every shape can move left or right. Therefore, Shape should contain the following functions:

public abstract class Shape {

    int x;
    int y;

    public void moveLeft(){
        this.x = x - 1;
    }

    ...

    abstract double getArea();
}

For the sake of brevity, I left out the other properties of a Shape. Imagine that it also has an up, down, right, and anything else that you want all shapes to have.

Now, we create an Oval.

public class Oval extends Shape {

    int height;
    int width;

    public Oval(int height, int width, int x, int y) {
        super(x, y);
        this.height = height;
        this.width = width;
    }

    public double getarea() { return Math.PI * width * height; }

}

Notice that we didn't have to tell an Oval how to move left or right. Because it extends a Shape, it already knows how to move left and right. In fact, we can tell our Ovals to move left and right just like this:

Oval o = new Oval(1, 1, 0, 0);
o.moveLeft();

Viola! Our Oval can move, even though we did not define a method called moveLeft inside of our Oval class. That is the beauty of inheritance - the moveLeft() method was inherited by our Oval.

Upvotes: 2

Arnaldo Ignacio Gaspar Véjar
Arnaldo Ignacio Gaspar Véjar

Reputation: 1277

You can use a parametrized class "Shape<T>" that have a concrete geometry called "GOval" or any others.

Consider this class

public class Shape<T> {

    T oval;
    public void moveLeft(){
            oval.move(-1,0);
  }
}

And its handler 

public class Oval extends Shape<GOval>{

    public Oval(int width,int height){
        oval = new GOval(0,0,width,height);
    }
}

Upvotes: 0

alkber
alkber

Reputation: 1436

Are you thinking about overriding super class moveLeft() ?

public class Oval extends Shape{

        GOval oval;
        public Oval(int width,int height){
            oval = new GOval(0,0,width,height);
        }

        @Override 
        public void moveLeft(){

             if (oval != null)
                oval.move(-1,0);

        }

    }

Upvotes: 0

J Steven Perry
J Steven Perry

Reputation: 1751

Try something like this:

public class Shape {
  // Now all Shapes can move()
  protected abstract void move(int x, int y);
  public void moveLeft(){
    //object?
    move(-1,0);
  }
}

public class Oval extends Shape {
  private GOval oval;
  public Oval(int width,int height) {
    oval = new GOval(0,0,width,height);
  }
  // Implement move()
  protected void move(int x, int y) {
    oval.move(x, y);// or whatever method on GOval makes it move()
  }
}

HTH

Upvotes: 2

Related Questions