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)
- OOP Concepts: Classes, objects, inheritance, polymorphism, encapsulation, abstraction
- 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
- Generics: Usage and wildcards
- Design Patterns: Singleton, Factory, Strategy, Observer, Dependency Injection (Intro)
- JDBC: Connecting with databases (CRUD operations), PreparedStatement, Connection pooling

Week 5-6: Spring Framework (Basics)

- Spring Core
- Dependency Injection (DI) and Inversion of Control (IoC)
- Beans, Scopes, and Bean Life Cycle
- Autowiring and Spring Annotations
- Spring AOP: Aspect-Oriented Programming fundamentals
- Spring Data JPA: Basic CRUD operations with JPA
- Entities, Repositories, and Custom Queries

Week 7: Spring Boot (Basics)

- Spring Boot Fundamentals: Understanding the Spring Boot architecture
- REST API creation
- Spring Boot Annotations (@RestController, @RequestMapping, etc.)
- Running a Spring Boot application
- Spring Boot Auto Configuration: Application properties and profiles
- Spring Boot with Database: Integrate Spring Boot with MySQL using Spring Data JPA

Week 8: Spring Boot (Advanced)

- Security: Introduction to Spring Security (Basic Authentication)
- Advanced Spring Boot Features: Exception handling (@ControllerAdvice)
- Logging with Spring Boot
- Pagination and Sorting
- Testing: Write unit tests using JUnit and Mockito in Spring Boot

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Java Backend Development is a highly in-demand and well-paying job in the tech industry.

If you're looking to become an excellent Java Developer, here's a roadmap that includes various online resources:

1. Core Java

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

https://youtube.com/playlist?list=PLd3UqWTnYXOnjGmyjD3zbIkyLXP15-6w0&si=UYvQhVNlZQYCH1Il

2. JDBC

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

https://youtube.com/playlist?list=PLsyeobzWxl7rU7Jz3zDRpqB-EODzBbHOI&si=Cc45vpeRXGIUKbfn

3. SQL

Get a good understanding of SQL, which is necessary to work with JDBC to write queries.

https://youtu.be/7S_tz1z_5bA

4. JSP + Servlet

Learn JSP and Servlet, which are used for writing web pages for web applications and handling client requests on the server-side.

https://youtube.com/playlist?list=PLE0F6C1917A427E96&si=TQeOIgluG3R29622

5. Spring Framework

5.1. Core Spring Framework

https://youtu.be/GB8k2-Egfv0?si=dHYp6rFkGVl9RMt8

5.2. Spring REST & Spring DATA

https://youtu.be/GwYUjzPrQTM?si=hJfmpukii2WnofxQ

5.3. Spring Security
Spring Security is the primary choice for implementing application-level security

https://youtu.be/sm-8qfMWEV8?si=uMkpBxOUXIptZif9

6. Hibernate Framework

Hibernate is a Java framework that simplifies the development of Java application to interact with the database. It is an open source, lightweight, ORM (Object Relational Mapping) tool.

https://youtu.be/Yv2xctJxE-w?si=q4FIOBxxX-Y0Qj5q

7. Spring Boot

Spring Boot is the ultimate framework and Makes Java Web Development less boilerplate, it can help you make production-ready applications in no time.

https://youtu.be/msXL2oDexqw?si=XB19MCCECAggcB18

8. Basic DevOps

8.1. Learn to Use AWS & Deploy Java Apps

https://youtube.com/playlist?list=PLVz2XdJiJQxxurKT1Dqz6rmiMuZNdClqv&si=bJyg0Np11PkGDIKO

8.2. Learn Basic Docker:

https://youtu.be/p28piYY_wv8?si=Xoqje7MJad1NeE9g

8.3. Learn Basic Kubernetes:

https://youtu.be/rTNR7vDQDD8?si=dgzwxQof7yGHUP4n

8.4. Deploy Spring Boot App on Kubernetes:

https://youtu.be/EZolJ4lNiYc?si=Kw09qKwMp_LxHTvw

9. Basic of git and GitHub
https://youtu.be/apGV9Kg7ics?si=MHtCgD8o7XqpU4W3

10. Java Microservices

https://youtu.be/tuJqH3AV0e8?si=1jjrWl4l4uYGrE5i

14. Java Quick revision for Interviews

https://youtu.be/oYXivKMSEqM?si=tngbZrvgbAwsShEb

15. Spring JMS(java messaging services)

JMS is a standard Java API that allows a Java application to send messages to another application.

https://youtube.com/playlist?list=PLmCsXDGbJHdibOx6axScPiuHA8ftsrmut&si=J0qjBSbB4GDCeTOv

𝐉𝐨𝐢𝐧 𝐭𝐡𝐢𝐬 𝐭𝐞𝐥𝐞𝐠𝐫𝐚𝐦 𝐠𝐫𝐨𝐮𝐩 𝐟𝐨𝐫 𝐩𝐫𝐞𝐦𝐢𝐮𝐦 Resources/Notes: https://t.iss.one/udacityfreecourse

C++ va Java

Java Roadmap
|
|-- Fundamentals
| |-- Basics of Programming
| | |-- Introduction to Java
| | |-- Java Development Kit (JDK) and Java Runtime Environment (JRE)
| | |-- Setting Up Development Environment (IDE: IntelliJ IDEA, Eclipse, etc.)
| |
| |-- Syntax and Structure
| | |-- Basic Syntax
| | |-- Variables and Data Types
| | |-- Operators and Expressions
|
|-- Control Structures
| |-- Conditional Statements
| | |-- If-Else Statements
| | |-- Switch Case
| |
| |-- Loops
| | |-- For Loop
| | |-- While Loop
| | |-- Do-While Loop
| |
| |-- Exception Handling
| | |-- Try-Catch Block
| | |-- Finally Block
| | |-- Throw and Throws Keywords
|
|-- Object-Oriented Programming (OOP)
| |-- Basics of OOP
| | |-- Classes and Objects
| | |-- Methods and Constructors
| |
| |-- Inheritance
| | |-- Single and Multiple Inheritance
| | |-- Method Overriding
| | |-- Super Keyword
| |
| |-- Polymorphism
| | |-- Method Overloading
| | |-- Runtime Polymorphism
| | |-- Dynamic Method Dispatch
| |
| |-- Encapsulation
| | |-- Access Modifiers (Public, Private, Protected)
| | |-- Getters and Setters
| | |-- Data Hiding
| |
| |-- Abstraction
| | |-- Abstract Classes
| | |-- Interfaces
|
|-- Advanced Java
| |-- Collections Framework
| | |-- List (ArrayList, LinkedList)
| | |-- Set (HashSet, TreeSet)
| | |-- Map (HashMap, TreeMap)
| | |-- Queue (PriorityQueue, LinkedList)
| |
| |-- Concurrency
| | |-- Multithreading (Creating Threads, Thread Lifecycle)
| | |-- Synchronization
| | |-- Concurrency Utilities (Executors Framework, Callable and Future, Locks and Semaphores)
|
|-- Java Standard Libraries
| |-- I/O Streams
| | |-- File Handling (File Class, Reading and Writing Files)
| | |-- Streams (Byte Streams, Character Streams, Buffered Streams)
| |
| |-- Networking
| | |-- Sockets (TCP and UDP, Socket and ServerSocket Classes)
| | |-- URL and HTTP (URL Class, HttpURLConnection)
| |
| |-- JDBC
| | |-- Database Connectivity (JDBC Drivers, Connection, Statement, and ResultSet)
| | |-- PreparedStatement and CallableStatement
|
|-- Java Frameworks
| |-- Spring Framework
| | |-- Spring Core (Dependency Injection, Inversion of Control)
| | |-- Spring MVC (Model-View-Controller Architecture)
| | |-- Spring Boot (Creating Spring Boot Applications, Starters and Auto-Configuration, Actuator)
| |
| |-- Hibernate
| | |-- ORM Basics (Introduction to ORM, Configuration and Mapping)
| | |-- Advanced Hibernate (Caching, Transactions and Concurrency, Criteria API)
|
|-- Web Development with Java
| |-- Java EE (Jakarta EE)
| | |-- Servlets (Lifecycle, Handling HTTP Requests and Responses, Session Management)
| | |-- JavaServer Pages (JSP) (Syntax, Directives, JSTL and Custom Tags, Expression Language)
| |
| |-- RESTful Web Services
| | |-- JAX-RS (Creating RESTful Services, Annotations and HTTP Methods, Consuming RESTful Services)
|
|-- Build Tools and Dependency Management
| |-- Maven
| | |-- Project Object Model (POM), Dependencies, Repositories, Build Lifecycle and Plugins
| |
| |-- Gradle
| | |-- Build Scripts, Dependency Management, Task Automation
|
|-- Testing in Java
| |-- Unit Testing
| | |-- JUnit (Annotations, Assertions, Test Suites and Runners)
| |
| |-- Mockito (Creating Mocks and Spies and Verification)
| |
| |-- Integration Testing
| | |-- Spring Test (Testing Spring Components and WebTestClient)
|
|-- Deployment and DevOps
| |-- Containers and Microservices
| | |-- Docker (Dockerfile, Image Creation, Container Management)
| | |-- Kubernetes (Pods, Services, Deployments, Managing Java Applications on Kubernetes)

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Typical java interview questions sorted by experience


Junior
* Name some of the characteristics of OO programming languages
* What are the access modifiers you know? What does each one do?
* What is the difference between overriding and overloading a method in Java?
* What’s the difference between an Interface and an abstract class?
* Can an Interface extend another Interface?
* What does the static word mean in Java?
* Can a static method be overridden in Java?
* What is Polymorphism? What about Inheritance?
* Can a constructor be inherited?
* Do objects get passed by reference or value in Java? Elaborate on that.
* What’s the difference between using == and .equals on a string?
* What is the hashCode() and equals() used for?
* What does the interface Serializable do? What about Parcelable in Android?
* Why are Array and ArrayList different? When would you use each?
* What’s the difference between an Integer and int?
* What is a ThreadPool? Is it better than using several “simple” threads?
* What the difference between local, instance and class variables?

Mid
* What is reflection?
* What is dependency injection? Can you name a few libraries? (Have you used any?)
* What are strong, soft and weak references in Java?
* What does the keyword synchronized mean?
* Can you have “memory leaks” on Java?
* Do you need to set references to null on Java/Android?
* What does it means to say that a String is immutable?
* What are transient and volatile modifiers?
* What is the finalize() method?
* How does the try{} finally{} works?
* What is the difference between instantiation and initialisation of an object?
* When is a static block run?
* Why are Generics are used in Java?
* Can you mention the design patterns you know? Which of those do you normally use?
* Can you mention some types of testing you know?

Senior
* How does Integer.parseInt() works?
* Do you know what is the “double check locking” problem?
* Do you know the difference between StringBuffer and StringBuilder?
* How is a StringBuilder implemented to avoid the immutable string allocation problem?
* What does Class.forName method do?
* What is Autoboxing and Unboxing?
* What’s the difference between an Enumeration and an Iterator?
* What is the difference between fail-fast and fail safe in Java?
* What is PermGen in Java?
* What is a Java priority queue?
* *s performance influenced by using the same number in different types: Int, Double and Float?
* What is the Java Heap?
* What is daemon thread?
* Can a dead thread be restarted?

Source: medium.

GitHub Cheatsheet

What is Encapsulation in java ?

📍 Encapsulation is one of the fundamental principle of object oriented programming .
📍 Encapsulation allows to protect the data within a class from outside entities.
📍 Encapsulation helps to achieve hiding the internal information from outside entities.
📍 Data and methods (To access the data) are bundled together within a single unit .(class)
📍 In Java, encapsulation is typically achieved by:
Declaring the class members as private.
Providing public getter and setter methods to access and modify the private attributes.
Note :
Let's say we have 1 private variables in a class

Example - 1:
getter & setter for primitive type private members.
private String empnm;

// get method to access the data
public String GetName() {
return empnm;
}

// set the data
public void setName(String enm) {
this.empnm = enm;
} // call the method & pass the data as param

If we can notice the getter & setter for empnm , below points we can note:
1. getter method will return the variable which is private and it is non parameterized .
2. setter method is a parameterized method which we shall use to set the value for the private member while calling , so only it is parameterized method.

Example -2 :getter & Setter for the private array :

public int[] getarr() {
return arr;
}

// Setter method to modify the private array
public void setarr(int[] brr) {
// You can add validation or other logic if needed
this.arr = brr;
}

Best Programming Resources: https://topmate.io/coding/886839

All the best 👍👍

Typical java interview questions sorted by experience


Junior
* Name some of the characteristics of OO programming languages
* What are the access modifiers you know? What does each one do?
* What is the difference between overriding and overloading a method in Java?
* What’s the difference between an Interface and an abstract class?
* Can an Interface extend another Interface?
* What does the static word mean in Java?
* Can a static method be overridden in Java?
* What is Polymorphism? What about Inheritance?
* Can a constructor be inherited?
* Do objects get passed by reference or value in Java? Elaborate on that.
* What’s the difference between using == and .equals on a string?
* What is the hashCode() and equals() used for?
* What does the interface Serializable do? What about Parcelable in Android?
* Why are Array and ArrayList different? When would you use each?
* What’s the difference between an Integer and int?
* What is a ThreadPool? Is it better than using several “simple” threads?
* What the difference between local, instance and class variables?

Mid
* What is reflection?
* What is dependency injection? Can you name a few libraries? (Have you used any?)
* What are strong, soft and weak references in Java?
* What does the keyword synchronized mean?
* Can you have “memory leaks” on Java?
* Do you need to set references to null on Java/Android?
* What does it means to say that a String is immutable?
* What are transient and volatile modifiers?
* What is the finalize() method?
* How does the try{} finally{} works?
* What is the difference between instantiation and initialisation of an object?
* When is a static block run?
* Why are Generics are used in Java?
* Can you mention the design patterns you know? Which of those do you normally use?
* Can you mention some types of testing you know?

Senior
* How does Integer.parseInt() works?
* Do you know what is the “double check locking” problem?
* Do you know the difference between StringBuffer and StringBuilder?
* How is a StringBuilder implemented to avoid the immutable string allocation problem?
* What does Class.forName method do?
* What is Autoboxing and Unboxing?
* What’s the difference between an Enumeration and an Iterator?
* What is the difference between fail-fast and fail safe in Java?
* What is PermGen in Java?
* What is a Java priority queue?
* *s performance influenced by using the same number in different types: Int, Double and Float?
* What is the Java Heap?
* What is daemon thread?
* Can a dead thread be restarted?

Source: medium.

Java for Everything: ☕

Java + Spring = Enterprise Applications

Java + Hibernate = Object-Relational Mapping

Java + Android = Mobile App Development

Java + Swing = Desktop GUI Applications

Java + JavaFX = Modern GUI Applications

Java + JUnit = Unit Testing

Java + Maven = Project Management

Java + Jenkins = Continuous Integration

Java + Apache Kafka = Stream Processing

Java + Apache Hadoop = Big Data Processing

Java + Microservices = Scalable Services

Best Programming Resources: https://topmate.io/coding/886839

All the best 👍👍