Chapter 8 Classes and Objects: A Deeper Look

The Time Object

Problem Description Time consists of hour (0 - 23), minute (0 - 59), and second (0 - 59). Develop the JTime class to represent time. JTime should have the following behaviors –Set a new time according to the new hour, minute, and second. Do not forget to validate these new values –Return a string to represent itself in the universal-time format: HH:MM:SS –Return a string to represent itself in the standard-time format: HH:MM:SS AM or PM

Questions 1.What is a valid hour? Minute? Second? 2.What is the universal-time format? 3.What is the standard-time format?

Answers 1.Valid hour: Valid minute: Valid second: Universal-time format: HH:MM:SS 3.Standard-time format: H:MM:SS AM or PM –If hour is 0 or 12, H will be 12. Otherwise, H will be (hour % 12) –If hour less than 12, it’s AM. Otherwise, it’s PM

Class Diagram

Developing the Constructor Without Input Data Validation

Adding Input Data Validation to the Constructor

Setting New Time

Getting the Universal-Time Format

Getting the Standard-Time Format

Exercise Compare our solution with the Deitel’s solution (in the next slides)

The Date Object

Problem Description Date consists of month (1 - 12), day (1 - 31), and year. Develop the JDate class and its constructor to represent a date. Do not forget to check the validity of input data Develop the toString() method for the JDate class according to the MM/DD/YYYY format

Question Q: How can we know that a year is leap year? A: A year is leap year if 1)It is divisible by 400, OR 2)It is divisible by 4 but not divisible by 100

Class Diagram To be filled

Step 1. Developing Constructor Without Input Validation

Validating the Month

Validating the Day

The Employee Object

Problem Description Info of an employee includes: First name, last name, birth date, and hire date. Develop the Employee class

Example First name: Sue Last name: Jones Birthday: Sept 5, 1986 Hire date: Jan 1, 2007

Class Diagram

A Better Design

An Even Better Design

Drawing Random Lines

Problem Draw a random number of lines (at least 1 and at most 5) inside a frame

Exercise Exercise 8.6

The Stock Problem A company’s stock consists of –The trading symbol. A short series of characters that are used to identify the stock on the stock exchange –The current price per share of the stock A stock purchase has the following information –The stock that was purchased –The number of shares Calculate the cost of the purchase

The Course Problem A course holds the following information: –The course name –The instructor’s last name, first name, and office number –The textbook’s title, author, and publisher

The Sports Car Problem A sports car has the following information: –The type (make) –The color –The price The type is either Porsche, Ferrari, or Jaguar The color is either red, black, blue, or silver

The Retail Problem An item in a retail store holds the following information –A brief description of the item –The number of units currently in inventory –The item’s retail price For example DescriptionUnits on HandPrice Item #1Jacket Item #2Designer Jeans Item #3Shirt

A cash register is a sale of a retail item Given the quantity of items being purchased, the cash register provides the sale’s subtotal, amount of sales tax, and total –The subtotal is the quantity multiplied by the price –The sales tax rate is 6% of a retail sale –The total is the subtotal plus the sales tax

The Parking Problem This problem is about a police officer issuing a parking ticket A parked car holds the following information –The car’s make (for example Toyota) –The model (for example, Nissan Z28) –The color –The license number (for example XY-1234) –The number of minutes that the car has been parked A parking meter records the number of minutes of parking time that has been purchased A parking ticket is responsible for –Reporting the make, model, color, and license number of the illegally parked car –Reporting the amount of the fine, which is $25 for the first hour or part of an hour that the car is illegally parked, plus $10 for every additional hour or part of an hour that the car is illegally parked –Reporting the name and badge number of the police officer issuing the ticket A police officer inspecting parked cars is responsible for –Telling his/her name and badge number –Examining the parked car and the parking meter, and determining whether the car’s time has expired –Issuing a parking ticket if the car’s time has expired