U - Unit Testing

Used to verify individual parts of code (methods, classes) using tools like JUnit or TestNG. Ensures each part works correctly in isolation.


V - Variables

Containers for storing data values. Java supports:

Instance variables
Static variables
Local variables
Parameters


W - Wrapper Classes

Provide object versions of primitive data types. E.g., int → Integer, double → Double. Useful when working with collections or for autoboxing.


X - XML (eXtensible Markup Language)

Used to store and transport data. In Java, XML is commonly used for configuration (e.g., Spring) and data interchange.


Y - Yield (Threading)

The Thread.yield() method hints to the scheduler that the current thread is willing to yield its current use of a processor.


Z - Zero-Based Indexing

Java arrays and collections are zero-indexed, meaning the first element is accessed at index 0.

int[] arr = {1, 2, 3};
System.out.println(arr[0]); // Outputs 1


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2 Month Roadmap to learn Java and Spring from basics to advanced

Week 1-2: Core Java

- Basic Syntax: Data types, operators, loops (for, while, do-while)
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- Collections Framework: List, Set, Map, Queue, Iterator, etc.
- Exception Handling: Try-catch, custom exceptions, multi-catch
- File I/O: Reading/writing files using java.io and java.nio
- Java 8+ Features: Lambdas, Streams, Optional, Functional Interfaces
- Multithreading: Threads, Runnable, ExecutorService, Future, and basic synchronization

Week 3-4: Advanced Java & JDBC

- JVM Internals: ClassLoader, JIT, memory management, garbage collection
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- JDBC: Connecting with databases (CRUD operations), PreparedStatement, Connection pooling

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- Spring Core
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Week 7: Spring Boot (Basics)

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1. Core Java

First comes the fundamentals of Java Programming, here you will understand OOP concepts, conditional statements, collection frameworks,and many more.

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2. JDBC

A  Java API that allows you to access tabular data, especially data stored in a relational database.

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5.2. Spring REST & Spring DATA

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8.1. Learn to Use AWS & Deploy Java Apps

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10. Java Microservices

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14. Java Quick revision for Interviews

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Java Basics every beginner should learn to build a strong foundation:

1. Hello World & Setup

Install JDK and an IDE (like IntelliJ or Eclipse)

Write your first program: public class HelloWorld

2. Data Types & Variables

Primitive types: int, double, char, boolean

Non-primitive types: String, Arrays, Objects

Type casting (implicit & explicit)

3. Operators

Arithmetic: + - * / %

Comparison: == != > < >= <=

Logical: && || !

4. Control Flow

If, else if, else

Switch-case

Loops: for, while, do-while

break and continue

5. Functions (Methods)

Syntax: public static returnType methodName(params)

Method overloading

Return types & parameter passing

6. Object-Oriented Programming (OOP)

Classes & Objects

this keyword

Constructors (default & parameterized)

7. OOP Concepts

Encapsulation (private variables + getters/setters)

Inheritance (extends keyword)

Polymorphism (method overriding)

Abstraction (abstract classes & interfaces)

8. Arrays & ArrayList

Declaring and iterating arrays

ArrayList methods: add, remove, get, size

Multidimensional arrays

9. Exception Handling

Try-catch-finally blocks

throw and throws

Custom exceptions

10. Basic Input/Output

Scanner class for user input

System.out.println() for output

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