DR.PRERNA SAXENA IT WOMEN SCIENTIST SANKALP SE SIDDHI FOUNDATION BHARAT ADVENTURE ISLAND GOOGLE.

Thursday, December 4, 2025

SUN JAVA BASICS

The term "Sun Java Basics" refers to the fundamental concepts of the Java programming language, as it was originally developed by Sun Microsystems (before being acquired by Oracle).

Here is an overview of the core concepts that define Java's foundation:

📜 Core Principles and Structure

1. The Java Platform

The Java platform is what makes Java applications highly portable ("Write Once, Run Anywhere").

Java Virtual Machine (JVM): The abstract machine that executes Java bytecode. It's the interpreter layer that translates bytecode into the native machine code of the underlying OS (Windows, macOS, Linux).
Java Runtime Environment (JRE): The minimal software required to run a Java application. It includes the JVM, core classes, and supporting files.
Java Development Kit (JDK): The full set of tools for developing Java applications. It includes the JRE, the compiler (javac), and other debugging/utility tools.

2. Execution Flow

You write source code in a .java file.
The Compiler (javac) converts the source code into bytecode in a .class file.
The JVM executes the bytecode.

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💡 Syntax and Language Fundamentals

1. Basic Structure

All executable Java code must be contained within a class. Execution begins in the main method.

Java
public class MyFirstProgram {
    public static void main(String[] args) {
        // Output statement
        System.out.println("Hello from Java!"); 
    }
}

2. Data Types

Java has two main categories of data types:

Category	Type	Description	Example
Primitive	`int`, `long`, `float`, `double`	Numeric values (integers and decimals).	`int count = 10;`
	`char`	A single Unicode character.	`char initial = 'S';`
	`boolean`	Represents `true` or `false`.	`boolean isComplete = true;`
Non-Primitive	`String`, Arrays, Classes	Reference types that hold memory addresses.	`String name = "Sun";`

3. Variables

Variables must be declared with their type before they can be used.

Declaration: int speed;
Initialization: speed = 60; or combined: int speed = 60;
Constants: Defined using the final keyword (e.g., final double PI = 3.14159;).

4. Operators

Arithmetic: +, -, *, /, % (modulo/remainder).
Relational: ==, !=, >, <, >=, <=.
Logical: && (AND), || (OR), ! (NOT).

🔁 Control Flow

These constructs determine the order in which statements are executed.

1. Decision Making

if-else: Executes a block if a condition is true.

Java
if (score >= 90) {
    System.out.println("Grade A");
} else {
    System.out.println("Not an A");
}

switch: Executes one block of code among many alternatives based on a single value.

2. Looping

for loop: Used when you know the number of iterations beforehand.

Java
for (int i = 0; i < 5; i++) {
    System.out.println(i); // Prints 0 to 4
}

while loop: Repeats a block of code as long as a condition is true.
do-while loop: Executes the loop body at least once, then checks the condition.

⚙️ Object-Oriented Programming (OOP)

Java is an OOP language, built around the concept of objects and classes.

Class: A blueprint for an object. It defines the structure (data/variables) and behavior (methods/functions) of its objects.
Object: An instance of a class. When you create an object, memory is allocated for it.

The four pillars of OOP are:

Encapsulation: The mechanism of binding the data (variables) and the code acting on the data (methods) together into a single unit (the class), and protecting the data from outside interference.
Inheritance: The process by which one class acquires the properties and methods of another class, promoting code reuse.
Polymorphism: The ability of an object to take on many forms. This is achieved through method overriding (redefining an inherited method) and method overloading (methods with the same name but different parameters).
Abstraction: Hiding complex implementation details and showing only essential information. This is achieved using abstract classes and interfaces.