Master Java

My experience coding Java in undergrad

Before Python, I used to program mainly in Java. And my highlight in my undergrad was :

1. Clearing Java Certification (Oracle Certified Professional Java Programming)

2. Creating an app.

The app was very basic. But it provided a valuable experience in terms of learning. And clearing OCPJP certification solidified my learning. And while I don’t use Java anymore and have switched to Python, I think these resources would be helpful for anyone using Java or wanting to learn Java. Sharing them below:

Some of the best youtube resources to learn from:

Programming with Mosh : Link

Java Telusko : Link

FreeCodeCamp : Link

MOOC Java :

Java Cheatsheets:

Cheatsheet 1: Link

Java Cheatsheet 2 : Link

Learning Java Roadmap :

Weeks 1–2: Java Basics & Object-Oriented Programming

• Topics:

  • Java syntax and structure

  • Primitive data types, variables, and arrays

  • Control flow (if, switch, loops)

  • Classes, objects, methods, constructors

  • Encapsulation and access modifiers

• Tasks:

  • Read Chapters 1–3 of OCP Study Guide by Jeanne Boyarsky & Scott Selikoff

  • You can combine this with solving Leetcode easy problems in Java to prepare for Interview

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Weeks 3–4: Inheritance, Polymorphism, and Interfaces

• Topics:

  • Inheritance and method overriding

  • super and this

  • Abstract classes and interfaces

  • Static and default interface methods

• Tasks:

  • Read Chapters 4–5 of OCP Study Guide by Jeanne Boyarsky & Scott Selikoff

  • Practice exam questions from sample test here

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Weeks 5–6: Core Java APIs

• Topics:

  • String, StringBuilder

  • Wrapper classes, Autoboxing

  • Java.util.Objects, equals, hashCode

• Tasks:

  • Read Chapter 6 of OCP Study Guide by Jeanne Boyarsky & Scott Selikoff.

  • Alternatively, you can use Youtube videos if that helps!

  • Implement custom equals and hashCode

  • LeetCode
    Filter by "String" tag for problems involving manipulation, reversal, substring checks, etc.

  • HackerRank – Java Strings
    Offers beginner to intermediate practice with Java syntax, including StringBuilder.

  • GeeksforGeeks – Java Wrapper Classes
    Read and then try coding exercises at the end of each article.

  • JavaPoint – Wrapper Class Quiz
    Quick MCQs to test understanding of autoboxing/unboxing behavior.

  • Exercism – Java Track
    Great for learning object-oriented programming concepts, including equals() and hashCode().

  • Edabit – Java Challenges
    Use custom class exercises to practice overriding methods like equals() and hashCode().

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Weeks 7–8: Exceptions, Lambdas, and Streams

• Topics:

  • Checked vs unchecked exceptions

  • Try-with-resources

  • Functional interfaces, Lambda expressions

  • Stream API basics and pipelines

• Tasks:

  • Read Chapters 7–8 of OCP Study Guide by by Jeanne Boyarsky & Scott Selikoff.

  • HackerRank – Java Exception Handling
    Practice identifying and handling different exception types.

  • GeeksforGeeks – Exception Handling in Java
    Includes conceptual explanations with hands-on code snippets and quizzes.

  • Java Code Examples – Try-with-resources
    Scroll to examples and challenges at the bottom of the article.

  • Exercism – Java File Handling
    Many exercises require file/resource handling, where you can apply try-with-resources.

  • HackerRank – Java Lambda Expressions
    Great intro-level challenge using Predicate, Consumer, etc.

  • JetBrains Academy – Java Functional Programming Track
    Offers interactive projects using lambdas and functional interfaces.

  • LeetCode – Stream-based Practice
    Not official, but many community problems use streams (look for functional solutions).

  • CodeGym – Streams and Lambda
    Has specific sections on Java 8 features with practical tasks.

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Weeks 9–10: Collections, Generics, and Nested Classes

• Topics:

  • List, Set, Map interfaces

  • Iterator, Comparable, Comparator

  • Generics syntax and wildcards

  • Static, non-static nested and inner classes

• Tasks:

  • Read Chapters 9–10 of OCP Study Guide by by Jeanne Boyarsky & Scott Selikoff.

  • Extensively use Leetcode to practice these as they are main data structures.

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Weeks 11–12: Concurrency, Modules, and I/O

• Topics:

  • Threads, Runnable, synchronization

  • ExecutorService

  • Java modules (Java 9+)

  • java.io and java.nio.file APIs

• Tasks:

  • Read Chapters 11–13

  • HackerRank – Java Threads
    Look for the day focused on threads (Java concurrency basics).

  • GeeksforGeeks – Multithreading in Java
    Each topic (e.g., Runnable, synchronized) has coding examples and practice questions.

  • Exercism – Java OOP/Concurrency Exercises
    Search exercises tagged with concurrency or OOP for threading logic.

  • Baeldung – ExecutorService Examples
    Follow the examples and try modifying tasks (fixed thread pool, scheduled executor, etc.).

  • JetBrains Academy (Hyperskill) – Java Multithreading Track
    Offers structured, project-based learning with ExecutorService.

  • CodeGym – Java Modules Tutorial with Practice
    Introduces module-info.java and project structure.

  • Baeldung – Java 9 Modules
    Offers guided tasks at the end of each article.

  • JetBrains Academy – Explore projects that use modular programming.

  • Exercism – File I/O Exercises
    Tasks involving reading/writing files with both java.io and java.nio.file.

  • HackerRank – Java File Reading
    Basic file reading and parsing practice.

  • Baeldung – Java I/O Guides
    Learn and modify working examples of Files.walk(), readAllLines(), etc.

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Weeks 13–14: Review and Practice

• Tasks:

  • Revisit weak areas

  • Use Enthuware or Whizlabs OCP mock tests

  • Redo practice questions from each chapter

  • Build mini-project (e.g., task tracker, file manager)

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Weeks 15–16: Full Mock Tests + Exam Readiness

• Tasks:

  • Take at least 4 full-length timed mock exams : Link

  • Analyze performance and review errors

  • Final revision of key concepts

  • Prepare exam-day logistics

Hope this is helpful!