Using Java MINISTRY OF EDUCATION & HIGHER EDUCATION COLLEGE OF SCIENCE AND TECHNOLOGY KHANYOUNIS- PALESTINE Lecture 6 Introduction to classes and objects

 What is Object-Oriented Programming ?  What classes, objects, methods ?  How to declare a class ?  How to use class to create an object?  How to declare methods in a class ?  Emank X Mezank 2 Presented & Prepared by: Mahmoud R. Alfarra

 It is a whole new way of thinking about programming!  It is a way of modeling software that maps your code to the real world.  Now please, Look in this room … 3 Presented & Prepared by: Mahmoud R. Alfarra What is Object-Oriented Programming ? Chair Door Man Window. No. of legs Material Color Size Purpose. Abstraction Encapsulation

4 Presented & Prepared by: Mahmoud R. Alfarra What is Object-Oriented Programming ? Any Thing Attributes Behavior Each one represented by variable in class Each one represented by method in class

 The terms class and object are often confused, and it is important to understand the distinction.  It may help you to visualize these terms using the earlier racecar analogy.  Think of a class as the template for the car, or perhaps the plans used to build the car.  The car itself is an instance of those plans, so it could be referred to as an object. 5 Presented & Prepared by: Mahmoud R. Alfarra What are classes, objects ?

6 Presented & Prepared by: Mahmoud R. Alfarra Classes, Objects ? Student Student Student Student Student car Car-AB-201 Car-AB-323 Car-BM-291 Objects classes

 The behavior of the class will be represented as a method in class.  The method can be declared as: 7 Presented & Prepared by: Mahmoud R. Alfarra What are methods ? Access_modifiers return_type method_name (arguments) { // instructions return value; }

8 Presented & Prepared by: Mahmoud R. Alfarra What are methods ? (Example) Public void add (int x, int y) { int sum = x + y; } Public int even (int x) { if (x%2 ==0) return x; else { JOptionPane.showMessageDialog(null, "The value is not even "); Return -1; } }

9 Presented & Prepared by: Mahmoud R. Alfarra How to declare Class? Access_modifiers class class_name{ //variables declaration // constructor // methods } Access_modifiers class class_name{ //variables declaration // constructor // methods } Public class Car{ public String model; public String ID; public int price; public Car (){ model = “Cevic”; ID = “ ”; price= 12,000; // methods } Public class Car{ public String model; public String ID; public int price; public Car (){ model = “Cevic”; ID = “ ”; price= 12,000; // methods }

10 Presented & Prepared by: Mahmoud R. Alfarra How to use class to create an object? class_name obj_name = new constructor_name (); Car c1 = new Car (); Car c2 = new Car (); c2.model = “Honda”; c2.ID = “987435”; c2.price = 4000; Car c2 = new Car (); c2.model = “Honda”; c2.ID = “987435”; c2.price = 4000;

قال الله تعالى‏:‏ ‏ (‏يوم تكون الجبال كالعهن المنفوش) 11 Presented & Prepared by: Mahmoud R. Alfarra

Equality and Relational Operators 12 Presented & Prepared by: Mahmoud R. Alfarra