Stacked canvas

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

enum Color {
    RED, GREEN, BLUE
}

interface Scalable{
    public void scale(float scaleFactor);
}

interface Stackable{
    public float weight();
}

abstract class Shape implements Scalable,Stackable{
    String id;
    Color color;
    Shape(){}
    Shape(String id, Color color){
        this.id=id;
        this.color=color;
    }
    abstract public void scale(float scaleFactor);
    abstract public float weight();
    abstract public String type();
}

class Circle extends Shape implements Scalable,Stackable{
    float radius;
    Circle(float r){
        super();
        radius=r;
    }

    Circle(String id, Color color, float radius){
        super(id,color);
        this.radius=radius;
    }

    public void scale(float scaleFactor) {
        radius*=scaleFactor;
    }
    public float weight() {
        return (radius*radius*(float)Math.PI);
    }

    public String type() {
        return "Circle";
    }

}

class Rectangle extends Shape implements Scalable,Stackable{
    float width,height;
    Rectangle(int w,int h){
        super();
        width=w;
        height=h;
    }

    Rectangle(String id, Color color, float width, float height){
        super(id,color);
        this.width=width;
        this.height=height;
    }
    public void scale(float scaleFactor) {
        width*=scaleFactor;
        height*=scaleFactor;
    }
    public float weight() {
        return (height*width);
    }

    public String type() {
        return "Rectangle";
    }

}

class Canvas{
    List<Shape> list;

    Canvas(){
        list=new ArrayList<>();
    }

    void add(String id, Color color, float radius) {
        if(list.size()==0) {
            list.add(new Circle(id,color,radius));
        }
        Circle c=new Circle(id,color,radius);
        for(int i=0;i<list.size();i++) {
            if(c.weight()>list.get(i).weight()) {
                list.add(i, c);
                return;
            }
        }
        if(c.weight()==list.get(list.size()-1).weight()) return;
        list.add(c);
    }

    void add(String id, Color color, float width, float height) {
        if(list.size()==0) {
            list.add(new Rectangle(id,color,width,height));
        }
        Rectangle r=new Rectangle(id,color,width,height);
        for(int i=0;i<list.size();i++) {
            if(r.weight()>list.get(i).weight()) {
                list.add(i, r);
                return;
            }
        }

        if(r.weight()==list.get(list.size()-1).weight()) return;
        list.add(r);
    }

    void scale(String id,float scaleFactor) {
        int index=-1;

        for(int i=0;i<list.size();i++) {
            if(list.get(i).id.equals(id)) {
                list.get(i).scale(scaleFactor);
                index=i;
                break;
            }
        }

        if(index==-1) return;

        if(list.get(index).type().equals("Circle")) {
            Circle c=(Circle)list.get(index);
            list.remove(index);
            this.add(c.id, c.color, c.radius);
        }
        if(list.get(index).type().equals("Rectangle")) {
            Rectangle r=(Rectangle)list.get(index);
            list.remove(index);
            this.add(r.id, r.color, r.width, r.height);
        }
    }

    public String toString() {
        StringBuilder sb=new StringBuilder();
        //System.out.println(list.size()+" size of list");
        for(Shape c:list) {

                if(c.type().equals("Circle")) {
                    sb.append(String.format("C: %-5s%-10s%10.2f\n", c.id,c.color, c.weight()));
                }
                if(c.type().equals("Rectangle")) {
                    sb.append(String.format("R: %-5s%-10s%10.2f\n", c.id,c.color, c.weight()));
                }
        }
        return sb.toString();
    }

}

public class ShapesTest {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Canvas canvas = new Canvas();
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine();
            String[] parts = line.split(" ");
            int type = Integer.parseInt(parts[0]);
            String id = parts[1];
            if (type == 1) {
                Color color = Color.valueOf(parts[2]);
                float radius = Float.parseFloat(parts[3]);
                canvas.add(id, color, radius);
            } else if (type == 2) {
                Color color = Color.valueOf(parts[2]);
                float width = Float.parseFloat(parts[3]);
                float height = Float.parseFloat(parts[4]);
                canvas.add(id, color, width, height);
            } else if (type == 3) {
                float scaleFactor = Float.parseFloat(parts[2]);
                System.out.println("ORIGNAL:");
                System.out.print(canvas);
                canvas.scale(id, scaleFactor);
                System.out.printf("AFTER SCALING: %s %.2f\n", id, scaleFactor);
                System.out.print(canvas);
            }

        }
    }
}