jdfive

Syllabus

Start with language foundations, then JVM and collections — the topics that show up most in backend interviews.

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Getting started

What Java is, install a JDK, write your first program, and understand a simple project layout.

  1. 1What Is Java
  2. 2JDK & First Program
  3. 3Project Layout

Language basics

Types, operators, control flow, methods, arrays, and strings — the grammar of every Java program.

  1. 4Variables & Types
  2. 5Operators
  3. 6Control Flow
  4. 7Methods
  5. 8Arrays
  6. 9Strings

Object-oriented Java

Classes, encapsulation, inheritance, interfaces, and the equals/hashCode contract.

  1. 10Classes & Objects
  2. 11Constructors
  3. 12Inheritance
  4. 13Abstract & Interfaces
  5. 14Packages & Access
  6. 15equals & hashCode
  7. 16Enums and Nested Types

Core APIs

Exceptions, generics, files, and java.time — the libraries you use every day.

  1. 17Exceptions
  2. 18Generics
  3. 19I/O and Files
  4. 20Dates and Time

Collections

Lists, sets, maps, and queues — pick the right structure and defend the choice.

  1. 21Collections Overview
  2. 22Lists
  3. 23Sets
  4. 24Maps
  5. 25Queues and Deques

Modern Java

Streams, Optional, records, and sealed types used in modern codebases.

  1. 26Streams API
  2. 27Optional
  3. 28Records & Sealed Types

JVM & runtime

How the JVM lays out memory, how garbage collection works, and which version features matter.

  1. 29Java Memory Structure
  2. 30Garbage Collection
  3. 31Versions Cheat Sheet

Concurrency

Threads, locks, concurrent collections, and virtual threads.

  1. 32Threads and Executors
  2. 33Sync & Visibility
  3. 34Concurrent Collections
  4. 35Virtual Threads

Wrap-up

A checklist of day-to-day skills and an interview topic map for what to revise next.

  1. 36Java Engineer Checklist