Basic Concepts of OOPs (Object Oriented Programming in Java)

Basic Concepts of OOPs (Object Oriented Programming in Java)

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  BASIC CONCEPTS OFOOPs Presented by: Michelle Anne Meralpis
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  JAVA • Java –a high-level programming language • Same with C, FORTRAN, Smalltalk, Perl • Lets you write special programs called Applets • Java is called as an Object-Oriented Programming Language
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  What is OOP? •Software Development Technique • Effective use of programmer productivity • Way of creating large scale systems • Approaching 100% solution
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  Basic Concepts ofOOPs • Object • Class • Inheritance • Polymorphism • Encapsulation • Data Abstraction
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  Object • A person,place or concepts • Composed of characteristics (data) and behavior (operation)
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  Example:
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  Class • A blueprintor prototype from which objects are created • A collection of objects of similar type
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  Example: Vehicle COST= 4,000,00 COLOR=RED Car MH-01 1234
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  Example:
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  Inheritance • The processby which objects of one class can get properties of objects of another class.
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  Polymorphism • The abilityto take more than one form • Allows us to write generic, reusable code more easily
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  Example:
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  Encapsulation • Wrapping ofdata and functions into a single unit (i.e. class) • Information hiding
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  Data Abstraction • Refersto the act of representing important description without including the background details or explanations
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  Creating Objects Point originOne= new Point(23,94); Rectangle rectOne = new Rectangle(originOne, 100, 200); Rectangle rectTwo = new Rectangle(50, 100); Each of these statements has three parts: 1. Declaration – the code set in bold are all variable declarations that associate a variable name with an object type. 2. Instantiation – the new keyword is a Java operator that creates the object. 3. Initialization: The new operator is followed by a call to a constructor, which initializes the new object.
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  Declaring Object Reference •Previously, you learned that to declare a variable, you write: type name; • You can also declare a reference variable on its own line. For example: Point originOne;
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  Instantiating a Class •The new operator returns a reference to the object it created. This reference is usually assigned to a variable of the appropriate type, like: Point originOne = new Point(23, 94); • It can also be used directly in an expression. For example: int height = new Rectangle().height;
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  Initializing an Object •Here's the code for the Point class: public class Point { public int x = 0; public int y = 0; //constructor public Point(int a, int b) { x = a; y = b; } }
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  Initializing an Object(2) Point originOne = new Point(23, 94); • The result of executing this statement can be illustrated in the next figure:
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  Calling an Object'sMethods • Append the method’s simple name to the object reference using intervening dot operator (.) • Provide arguments to the method within enclosing parenthesis () objectReference.methodName(argumentList); Or objectReference.methodName();
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  Calling an Object'sMethods (2) new Rectangle(100, 50).getArea() • As shown, you can use the dot notation to invoke the new Rectangle’s getArea() method to compute the area of the new rectangle.