AP Computer Science Exam Question

Consider the following Rectangle class:

public class Rectangle {
    private int length;
    private int width;
    
    public Rectangle(int length, int width) {
        this.length = length;
        this.width = width;
    }
    
    public int getLength() {
        return length;
    }
    
    public int getWidth() {
        return width;
    }
    
    public void setLength(int length) {
        this.length = length;
    }
    
    public void setWidth(int width) {
        this.width = width;
    }
    
    public int calculateArea() {
        return length * width;
    }
}

1. Modify the Rectangle class to include an instance variable color of type String. Provide appropriate getter and setter methods for color.

2. Suppose you have two Rectangle objects rect1 and rect2 with lengths 5 and 7 respectively, and widths 3 and 4 respectively. Write a code snippet to:

   • Set the color of rect1 to "blue".
   • Set the color of rect2 to "green".
   • Calculate and store the area of rect1 in a variable called area1.
   • Calculate and store the area of rect2 in a variable called area2.

3. Suppose you have a Square class that extends the Rectangle class. The Square class should have a single parameter constructor that takes an integer side length and calls the superclass constructor to set both the length and width equal to the side length. Implement the Square class accordingly.

4. Write code to create a Square object square1 with side length 6, and set the color of square1 to "yellow". Calculate and store the area of square1 in a variable called areaSquare1.

Note: Assume that the necessary import statements are already included.

Answer

1. Modified Rectangle class:

public class Rectangle {
    private int length;
    private int width;
    private String color;
    
    public Rectangle(int length, int width) {
        this.length = length;
        this.width = width;
    }
    
    public int getLength() {
        return length;
    }
    
    public int getWidth() {
        return width;
    }
    
    public void setLength(int length) {
        this.length = length;
    }
    
    public void setWidth(int width) {
        this.width = width;
    }
    
    public String getColor() {
        return color;
    }
    
    public void setColor(String color) {
        this.color = color;
    }
    
    public int calculateArea() {
        return length * width;
    }
}

2. Code snippet to set color and calculate area:

public class Main {
    public static void main(String[] args) {
        Rectangle rect1 = new Rectangle(5, 3);
        Rectangle rect2 = new Rectangle(7, 4);
        
        rect1.setColor("blue");
        rect2.setColor("green");
        
        int area1 = rect1.calculateArea();
        int area2 = rect2.calculateArea();
    }
}

3. Square class:

public class Square extends Rectangle {
    public Square(int sideLength) {
        super(sideLength, sideLength);
    }
}

4. Code snippet to create Square object:

public class Main {
    public static void main(String[] args) {
        Square square1 = new Square(6);
        square1.setColor("yellow");
        
        int areaSquare1 = square1.calculateArea();
    }
}

In the solution, we modified the Rectangle class to include the color instance variable and the corresponding getter and setter methods. We also created a Square class that extends the Rectangle class and implemented a constructor to set both the length and width equal to the side length. Finally, we created objects and performed color setting and area calculation operations as required.