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If this code was written in C++, what keyword would need to precede the declaration of the draw() method in the Shape class in order to allow polymorphism?

If this code was written in C++, what keyword would need to precede the declaration of the draw() method in the Shape class in order to allow polymorphism?

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Complete the code to create a polymorphism situation.

If this code was written in C++, what keyword would need to precede the declaration of the draw() method in the Shape class in order to allow polymorphism?
Transcribed Image Text:If this code was written in C++, what keyword would need to precede the declaration of the draw() method in the Shape class in order to allow polymorphism?
**Text Description:** *Shape* is a superclass with subclasses *Circle, Rect*, etc. Assume that *Shape* has a `draw()` method that does nothing, and that *Circle* and *Rect* each have a `draw()` method that draws a circle and rectangle, respectively. Consider the following code: ```java Circle c1 = new Circle(Color.BLUE, 100,100, 50); Rect r1 = new Rect (Color.GREEN, 200,100, 50,50); c1.draw(); r1.draw(); Shape s1 = c1, s2 = r1, s3; s1.draw(); s2.draw(); ``` **Explanation:** This segment of code demonstrates the concepts of inheritance and polymorphism in object-oriented programming. The `Shape` class acts as a base class, while `Circle` and `Rect` are derived classes, each implementing a specific version of the `draw()` method. 1. **Declarations:** - `Circle c1 = new Circle(Color.BLUE, 100,100, 50);` - Creates a new `Circle` object `c1` with the color blue and specific dimensions. - `Rect r1 = new Rect (Color.GREEN, 200,100, 50,50);` - Creates a new `Rect` object `r1` with the color green and specific dimensions. 2. **Method Invocation:** - `c1.draw();` and `r1.draw();` call the `draw()` method for each respective object, invoking the action to draw a circle and a rectangle. 3. **Polymorphism:** - `Shape s1 = c1, s2 = r1, s3;` - `s1` and `s2` are declared as `Shape` type references that point to `c1` and `r1`, respectively. - `s1.draw();` and `s2.draw();` - Although `s1` and `s2` are of type `Shape`, they call the overridden `draw()` methods in `Circle` and `Rect`, demonstrating polymorphism. This code block illustrates how object-oriented programming leverages class hierarchies and method overriding to achieve flexible design patterns.
Transcribed Image Text:**Text Description:** *Shape* is a superclass with subclasses *Circle, Rect*, etc. Assume that *Shape* has a `draw()` method that does nothing, and that *Circle* and *Rect* each have a `draw()` method that draws a circle and rectangle, respectively. Consider the following code: ```java Circle c1 = new Circle(Color.BLUE, 100,100, 50); Rect r1 = new Rect (Color.GREEN, 200,100, 50,50); c1.draw(); r1.draw(); Shape s1 = c1, s2 = r1, s3; s1.draw(); s2.draw(); ``` **Explanation:** This segment of code demonstrates the concepts of inheritance and polymorphism in object-oriented programming. The `Shape` class acts as a base class, while `Circle` and `Rect` are derived classes, each implementing a specific version of the `draw()` method. 1. **Declarations:** - `Circle c1 = new Circle(Color.BLUE, 100,100, 50);` - Creates a new `Circle` object `c1` with the color blue and specific dimensions. - `Rect r1 = new Rect (Color.GREEN, 200,100, 50,50);` - Creates a new `Rect` object `r1` with the color green and specific dimensions. 2. **Method Invocation:** - `c1.draw();` and `r1.draw();` call the `draw()` method for each respective object, invoking the action to draw a circle and a rectangle. 3. **Polymorphism:** - `Shape s1 = c1, s2 = r1, s3;` - `s1` and `s2` are declared as `Shape` type references that point to `c1` and `r1`, respectively. - `s1.draw();` and `s2.draw();` - Although `s1` and `s2` are of type `Shape`, they call the overridden `draw()` methods in `Circle` and `Rect`, demonstrating polymorphism. This code block illustrates how object-oriented programming leverages class hierarchies and method overriding to achieve flexible design patterns.
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