Java Programming Last Day Revision Notes + Important Questions (BCA) Exam Ready

Java Programming
Last Day Revision Notes

BCA — Bachelor of Computer Applications




8 12 25+ 100%
Core Topics Important Questions Code Examples Exam Ready




Contents

■
Java Basics — Features, Data Types, Control Flow
01

■
OOP Concepts — 4 Pillars, Classes, Constructors
02

■
Inheritance — Types, Overriding, Polymorphism
03

■
Abstract Classes & Interfaces
04

■
Exception Handling — try-catch, throw/throws
05

■
Strings & Arrays — Methods, StringBuilder
06

■
Multithreading — Lifecycle, Synchronization
07

■
Collections — List, Set, Map, Queue
08

■
Important Exam Questions (2 & 5 marks)
09

, 01 — Java Basics


Java Key Features
• Platform Independent — compiled to bytecode (.class), runs on any JVM
• Object-Oriented — everything is an object (except primitives)
• Strongly Typed — every variable must be declared with a type
• Automatic Memory Management — Garbage Collector frees unused objects
• Multithreaded — built-in support for concurrent execution
• Secure & Robust — no pointers, exception handling, type checking

Note: JDK = JRE + compiler tools. JRE = JVM + libraries. JVM actually runs the bytecode.



Primitive Data Types Access Modifiers & Key Keywords

• byte — 1 byte (−128 to 127) • public — accessible everywhere

• short — 2 bytes • private — only within same class

• int — 4 bytes (most used) • protected — same package + subclasses

• long — 8 bytes (suffix: L) • default (no keyword) — same package only

• float — 4 bytes (suffix: f) • ■■■■■■■■■■■■■■■■■■■■■

• double — 8 bytes (default decimal) • static — belongs to class, not instance

• char — 2 bytes (Unicode) • final — constant / no override / no inherit

• boolean — true / false • this — current object reference

• super — parent class reference



Basic Program Structure
public class Hello {

public static void main(String[] args) {

// entry point of every Java program

System.out.println("Hello, World!");

int x = 10; // integer variable

double pi = 3.14; // decimal variable

String name = "BCA"; // reference type

// Type casting

int a = (int) pi; // explicit: double -> int (data loss possible)

double b = x; // implicit: int -> double (widening, safe)

, }

}




Control Flow Quick Reference
// if-else

if (x > 0) { ... } else if (x == 0) { ... } else { ... }

// switch

switch (day) {

case 1: System.out.println("Monday"); break;

default: System.out.println("Other");

}

// for loop

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

// while loop

while (i < 5) { ... }

// do-while loop

do { ... } while (i < 5);

// enhanced for (for-each)

for (String s : names) { ... }