Objektorienteeritud programmeerimine (Narva Kolledž) 2018/19 kevad

slides_s3.pdf

slides 1-35 by Adil Aslam

Task 1. Devices

Object class Device has private instance fields: code (int), name (String) and price without the sales tax (double). In addition, the object class has a static field (double) for the sales tax (in percent). The sales tax in Estonia is 20%. Moreover, the object class should have a constructor and the following methods:

• get and set methods for all instance fields;
• method priceWithTax (double) which returns the total price of the item (item price + the sales tax)
  • e.g. if the price without the sales tax is 100€, then the price with the tax is 120€;
• method toString which returns info about the item in a readable way:
  • e.g. item name and its price with the sales tax is 120€.

In the main class, create several devices. Print info about them.

Task 2. Static mess

Try to run the following code:

public class Person {
  private String name;
  private double height;  // in meters
 
  public Person(String personName, double personHeight) {
    name = personName;
    height = personHeight;
  }
 
  // ski length in cm
  public int skiLength() {
    return (int) Math.round(0.85 * height * 100);
  }
 
  public static void main(String[] args) {
    System.out.println("The length of the ski is " + skiLength());
  }
}

Why hasn’t it been compiled? Change the code so that it could be compiled.

Task 3. Flights

1. Object class Plane has private instance fields: name (String), average speed (double) and maximum number of passengers (int). The object class has also a constructor and the following instance methods:

• get and set methods for all the instance fields;
• method toString which returns info about the plane in a readable way.

2. Object class Flight has private instance fields: destination (String), distance to the destination (int), plane (Plane) and the number of sold tickets (int). The object class has a constructor and the following instance methods:

• all the instance fields have get and set methods;
• a method (int) which returns the duration of the flight in minutes (use the average speed of the plane to calculate the duration of the flight);
• a method (int) which returns the number of free seats in the plane (use the number of sold tickets and the maximum number of passengers in the plane);
• method toString which returns info about the flight in a readable way.

3. In the main class, create at least three flights and at least two planes:

• e.g. Fokker 50 whose average speed is 530 km/h and the maximum number of passengers is 46; BN-2 whose average speed is 170 km/h and the maximum number of passengers is 9.

4. In the main class, demonstrate the use of different instance methods.