Object-Oriented vs Procedure-Oriented Programming

Procedure-Oriented Programming (POP)

• Focuses on organizing a program into functions or procedures
• Each procedure performs a specific task

Console Programming

• Uses text-only interfaces

Swing Programming

• Creates graphical user interfaces (GUIs)

Object-Oriented Programming (OOP)

• Uses objects as building blocks for software development
• Objects represent real-world entities

Key Differences: OOP vs. POP

• Organization:
  • OOP: Data and functions are encapsulated within objects
  • POP: Data and functions are separate
• Reusability:
  • OOP: Objects can be reused and extended through inheritance, classes are reused and extended
  • POP: Functions can be reused, but managing related data requires more manual effort
• Maintainability:
  • OOP: Encapsulation and modularity make code easier to maintain
  • POP: Managing and understanding data flow can be complex as the program grows

Key Concepts of OOP

• Encapsulation: Bundling attributes and methods within one unit
• Inheritance: One class inheriting properties and behaviors from another class
• Polymorphism: Different objects responding to the same function call in different ways
• Abstraction: Hiding implementation details, only displaying necessary features
• Modularity: Coding and understanding specific parts of the system without needing to understand the entire system
• Reusability: Flexibility of reusing programs
• Constructor: A method used to initialize object attributes when an object is created

Classes

• A blueprint or template for creating objects
• Defines structure (attributes) and behavior (methods) of objects

Superclasses

• Base class, ancestor class

Subclasses

• Derived class, descendant class, child class

Non-Static Class

• Requires instantiation

Static Class

• Doesn't require instantiation

Objects

• An instance of a class
• Possesses attributes and behaviors
• Each object can have unique attribute values

Attributes

• Variables within a class that represent the state or characteristics of objects
• Store data that can be manipulated by methods

State

• The current values of object attributes
• State can change as an object interacts with methods

Methods

• Actions performed by an object
• Functions defined within a class that specify object behavior

Abstract Methods

• Empty methods

Interfaces

• A collection of methods indicating a class has specific behavior beyond its inherited properties
• Defines a common set of methods that classes can implement

Types of Methods

• Instance Method: Operates on an object (instance of the class)
• Static Method: Belongs to the class, not an instance; called on the class itself

Packages

• Group related classes and interfaces in a structured way
• Enable access only to needed groups of classes
• Eliminate potential conflicts among class names

Instantiation

• Process of creating an object from a class
• Example:
  • MyClass objectAko = new MyClass();

Scanner Class

• Reads user input from the java.util package
• Declare an input Scanner in the main method to use Scanner class methods
• Syntax:
  • Scanner scan = new Scanner(System.in);
• Methods:
  • nextLine(): Reads a String
  • nextInt(): Reads an integer
  • nextDouble(): Reads a double
  • nextFloat(): Reads a float
  • nextBoolean(): Reads a boolean
  • nextByte(): Reads a byte
  • nextLong(): Reads a long integer
  • nextShort(): Reads a short integer

BufferedReader Class

• Reads user input from the java.io package
• Syntax:
  • BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
• Methods:
  • read(): Reads a single character
  • readLine(): Reads a line of text

Comments in Java

• Single Line: //
  • Example: // defines a class named HelloWorld
• Multi-Line: /* */
  • Example:
    • public class SampleNo1 // defines a class named SampleNo1 { public static void main (String [ ] args) { System.out.println (“ Java is fun! “); System.out.print (“ Let’s enjoy learning it!”); } // end of main } // end of class

public static void main(String[] args) Method

• Entry point to the program for the JVM
• public: Accessible by other methods in the code
• static: Automatically executed by the Java VM
• void: Doesn't return any value
• main: Name of the method
• (String[] args): Accepts an array of strings as arguments

System.out.println()

• Used to send output to the screen
• System.out is the object used for sending output
• println() is the method used to send the output
• The item(s) in parenthesis are arguments which provide information for the method to carry out its action
• println() prints the output and then moves to a new line