CSE205 Lecture 09

Object-Oriented Programming and Data Structures
Polymorphism
(202202)

Transcript

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   CSE 205
   Object-Oriented Programming and
   Data Structures
   Lecture 09: Polymorphism
   Dr. Javier Gonzalez-Sanchez
   javiergs@asu.edu
   javiergs.engineering.asu.edu | javiergs.com
   PERALTA 230U
   Office Hours: By appointment
   

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2. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 2
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   Homework 01
   § See description on Canvas. It is all about inheritance, abstract (class and
   method), and polymorphism.
   § Due date: You have a week to accommodate to your needs, but you do not
   need a full week to complete it. No extensions
   

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   Polymorphism
   

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4. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 4
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   Polymorphism
   § A polymorphic reference is a reference variable that can refer to different
   types of objects at different points in time.
   § Polymorphic references are resolved at run-time, not during compilation.
   

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5. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 5
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   Abstract Methods
   

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6. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 6
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   Polymorphism
   

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7. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 7
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   Polymorphism
   

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8. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 8
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   Polymorphism
   

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   Test Yourselves I
   

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10. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 10
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    Scenario
    

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11. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 11
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    Shape
    public abstract class Shape {
    protected double size;
    public Shape (double s) {size = s;}
    public abstract double area();
    }
    

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12. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 12
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    Square
    public class Square extends Shape {
    public Square (double s) {
    super(s);
    System.out.println("A Square is born");
    }
    public double area() { return size * size;}
    }
    

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13. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 13
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    Circle
    public class Circle extends Shape {
    public Circle (double s) {
    super(s);
    System.out.println("A Circle is born");
    }
    public double area() { return Math.PI * size * size;}
    }
    

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14. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 14
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    Triangle
    public class Triangle extends Shape {
    public Triangle (double s) {
    super(s);
    System.out.println("A Triangle is born");
    }
    public double area() { return size * size / 2;}
    }
    

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15. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 15
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    Main
    public class Main {
    public static void main(String[] a) {
    Shape shape1, shape2, shape3;
    shape1 = new Triangle(5);
    System.out.println(shape1.area());
    shape2 = new Square(5);
    System.out.println(shape2.area());
    shape3 = new Circle(5);
    System.out.println(shape3.area());
    }
    }
    

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16. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 16
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    Output
    

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    Object Class
    

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18. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 18
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    The Class Object
    § The Object class is a special class defined in the java.lang package.
    § All classes are derived from the Object class.
    

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19. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 19
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    Conversions
    

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20. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 20
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    getClass
    

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21. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 21
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    getClass
    

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22. Javier Gonzalez-Sanchez | CSE205 | Fall 2021 | 22
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    Questions
    

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    CSE 205 Object-Oriented Programming and Data Structures
    Javier Gonzalez-Sanchez, Ph.D.
    javiergs@asu.edu
    Fall 2021
    Copyright. These slides can only be used as study material for the class CSE205 at Arizona State University.
    They cannot be distributed or used for another purpose.
    

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