📘

Java Lecture 2: Exploring a Java Program

Jul 23, 2024

Lecture 2: Java Programming Language

Key Points

Focus: Exploring a Java program.
Previous Lecture Recap: Introduction to Java, including its history, compilation, and execution.

Case Sensitivity

Java is case-sensitive like C and C++.
Small and capital letters are considered different.

Object-Oriented Nature

Nearly 100% Object-Oriented: Java is near 100% object-oriented, unlike C++ which allows non-OOP coding.
Everything as Objects: Data must be represented in terms of objects.

Java vs. C++ Functions

Java: All functions must be members of a class. No non-member functions.
C++: Both member and non-member functions are allowed.

First Java Program Analysis

**Class Declaration: **The program starts with declaring a public class.

Example Program: Analyzing 'Hello World'

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World");
    }
}

Public Keyword: Used before the class name. Only outer classes can be public or default (no keyword).
Class Keyword: Defines a new class. Allows encapsulation of properties and methods.
Camel Notation: Class names follow camel case; first letter of every word is capitalized (e.g., HelloWorld).
Curly Braces & Semicolon: Class declaration doesn't need a semicolon like in C++.

Main Function

As Member Function: Unlike C++, the main function in Java is always part of some class.
Prototype: The main function follows a fixed prototype: public static void main(String[] args).
Public: Accessible from outside the class by JVM.
Static: Doesn't require an instance of the class to be called.
Void: Does not return a value.
String Args: Command-line arguments passed as an array of strings.

Printing in Java

System.out.println: Used to print text to the console.
System: A class in Java with properties and methods for basic system operations.
Out: A static member of the System class, often used for standard output.
println: Prints the given string and moves to a new line.
print: Similar to println but does not move to a new line.

Summary

Understanding Differences: Understanding minor differences between Java and C++ helps in learning Java effectively.
**Key Points: **Remember public, static, and void keywords for writing a basic Java program.
Camel Notation: Use camel case for class names and follow Java specific syntax for writing functions and printing statements.

End of Lecture Notes

Full transcript