Abhishek Gupta

Posted on May 2

🚀 Java Crash Course (CIITM Dhanbad BCA 4th Sem) — From Zero to Exam Ready

Didn’t study Java all semester?
This guide will take you from zero → exam-ready → confident pass in a few days.

🎯 HOW TO USE THIS

Day 1 → Unit 1
Day 2 → Unit 2
Day 3 → Unit 3
Day 4 → Unit 4 + 5
Day 5 → Revision

👉 Focus on VVI ⭐⭐⭐⭐ topics

🧠 UNIT I — JAVA BASICS

✅ C++ vs Java (VVI ⭐⭐⭐⭐)

Short Para:
Java is platform-independent and secure, while C++ is platform-dependent and faster but less secure.

C++	Java
Platform dependent	Platform independent
Uses pointers	No pointers
Manual memory	Automatic (Garbage Collection)

✅ Java & Internet / WWW

Short Para:
Java is widely used for web development and works well with internet applications using browsers and servers.

✅ Java Environment

📌 Includes:

JDK (Java Development Kit)
JRE (Java Runtime Environment)
JVM (Java Virtual Machine)

✅ JVM (VVI ⭐⭐⭐⭐)

Short Para:
JVM is a virtual machine that runs Java bytecode and makes Java platform-independent.

✅ Java Program Structure

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

✅ Tokens

📌 Smallest unit of Java:

Keywords
Identifiers
Literals
Operators

✅ Data Types

int, float, char, boolean

✅ Variables & Constants

Variable → value changes
Constant → fixed value (final)

✅ Type Casting

int a = (int) 10.5;

✅ Operators

Arithmetic → + - *
Relational → > <
Logical → && ||
Assignment → =

✅ Decision Making

if(x > 0) {
    System.out.println("Positive");
}

✅ Loops (VVI ⭐⭐⭐⭐)

for(int i=0; i<5; i++) {
    System.out.println(i);
}

✅ Jump Statements

break → exit loop
continue → skip iteration

✅ Labeled Loop

outer:
for(int i=0;i<3;i++){
    for(int j=0;j<3;j++){
        break outer;
    }
}

🧠 UNIT II — OOP IN JAVA (MOST IMPORTANT)

✅ Class & Object (VVI ⭐⭐⭐⭐)

Short Para:
Class is a blueprint, object is its instance.

class Student {
    int age;
}

✅ Constructors

Student() {
    System.out.println("Constructor");
}

✅ Method Overloading

Same method name, different parameters

✅ Static Members

Shared by all objects

✅ Inheritance (VVI ⭐⭐⭐⭐)

class A {}
class B extends A {}

✅ Method Overriding

Child class modifies parent method

✅ Final Keyword

final variable → constant
final method → cannot override
final class → cannot inherit

✅ Abstract Class

Cannot create object

✅ Visibility Control

public
private
protected

🧠 UNIT III — ARRAYS, INTERFACES, PACKAGES

✅ Arrays (VVI ⭐⭐⭐⭐)

int arr[] = {1,2,3};

✅ 2D Array

int arr[][] = {{1,2},{3,4}};

✅ Strings

String s = "Java";

✅ Vector

Dynamic array

✅ Wrapper Classes

Convert primitive → object
Example: Integer, Double

✅ Interfaces (VVI ⭐⭐⭐⭐)

interface A {
    void show();
}

✅ Packages

Used to organize classes

🧠 UNIT IV — THREADS

✅ Thread

Short Para:
Thread is a lightweight process used for multitasking.

✅ Creating Thread

class A extends Thread {
    public void run() {
        System.out.println("Thread");
    }
}

✅ Life Cycle

New
Runnable
Running
Dead

✅ Synchronization

Used to control multiple threads

✅ Runnable Interface

Alternative way to create thread

🧠 UNIT V — APPLETS

✅ Applet

Short Para:
Applet is a Java program that runs inside a web browser.

✅ Applet vs Application

Applet	Application
Runs in browser	Runs standalone
Needs HTML	No HTML

✅ Applet Life Cycle

init()
start()
stop()
destroy()

✅ Applet Tag

<applet code="Test.class" width="300" height="300"></applet>

✅ Passing Parameters

Using HTML tag

✅ Getting Input

Using UI elements

🔥 MUST PREPARE (HIGH SCORE)

C++ vs Java ⭐⭐⭐⭐
JVM ⭐⭐⭐⭐
Loops ⭐⭐⭐⭐
Class & Object ⭐⭐⭐⭐
Inheritance ⭐⭐⭐⭐
Interfaces ⭐⭐⭐⭐
Arrays ⭐⭐⭐⭐
Threads ⭐⭐⭐⭐
Applet Life Cycle ⭐⭐⭐⭐

📅 5-DAY PLAN

Day 1 → Unit 1
Day 2 → Unit 2
Day 3 → Unit 3
Day 4 → Unit 4 + 5
Day 5 → Revision

🚀 FINAL MESSAGE

You don’t need full semester study.
You need smart revision + important topics.

👉 Read this 2–3 times
👉 Practice key programs
👉 Go confident