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Tuesday, 30 August 2016

Chapter 9 Exercise 1, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

9.1 (The Rectangle class) Following the example of the Circle class in Section 9.2,
design a class named Rectangle to represent a rectangle. The class contains:

  • Two double data fields named width and height that specify the width and
  • height of the rectangle. The default values are 1 for both width and height .
  • A no-arg constructor that creates a default rectangle.
  • A constructor that creates a rectangle with the specified width and height .
  • A method named getArea() that returns the area of this rectangle.
  • A method named getPerimeter() that returns the perimeter.

Draw the UML diagram for the class and then implement the class. Write a test
program that creates two Rectangle objects—one with width 4 and height 40
and the other with width 3.5 and height 35.9 . Display the width, height, area,
and perimeter of each rectangle in this order.


public class MyRec2 {

    private double width;
    private double height;

    public MyRec2() {
        this.width = 1.0;
        this.height = 1.0;
    }

    public MyRec2(double width, double height) {
        this.width = width;
        this.height = height;
    }

    /** return area **/
    public double getArea() {
        return this.width * this.height;
    }
    /** return perimeter **/
    public double getPerimeter() {
        return this.width * 2 + this.height * 2;
    }

}
public class Exercise_01 {

    public static void main(String[] args) {


        MyRec2[] rectangles = new MyRec2[2];
        rectangles[0] = new MyRec2(4,40);
        rectangles[1] = new MyRec2(3.5, 35.9);

        for (int i = 0; i < 2; i++){
            System.out.println("MyRec2 " + (i+1) +":");
            System.out.print("Area = " + rectangles[i].getArea());
            System.out.println(" Perimeter = " +  rectangles[i].getPerimeter() +"\n");
        }
    }
}

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