Seven things that make you a
real Java developer
You know Java syntax. You can write classes, loops, and methods. This portal covers the six topics that separate someone who knows Java from someone who works in Java — the things every professional codebase uses daily.
Prerequisite: Java beginner course complete — variables, OOP, collections, exceptions, file I/O
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Module 1
Generics
Write type-safe classes and methods that work with any type. Understand how ArrayList<T>, HashMap<K,V> and all Java collections actually work under the hood.
type parametersbounded typeswildcardsgeneric methods
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Module 2
Lambdas & Streams
The modern Java way to process collections. Write filter, map, and collect operations that replace verbose loops with expressive one-liners used in every professional codebase.
lambda syntaxfunctional interfacesStream APIcollectors
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Module 3
Enums & Records
Cleaner, safer data types. Enums replace error-prone String constants. Records eliminate boilerplate data classes. Both are used constantly in modern Java codebases.
enum methodsenum with fieldsrecordspattern matching
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Module 4
Optional
Eliminate NullPointerExceptions by design. Optional forces you to handle the "value might not exist" case explicitly, making your code's intent clear and your APIs safer.
Optional.of / emptymap & flatMaporElse patternsnull design
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Module 5
Concurrency Basics
Make your programs do multiple things at once. Understand threads, the risks of shared state, and how ExecutorService makes writing safe concurrent code manageable.
Thread & Runnablerace conditionssynchronizedExecutorService
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Module 6
Design Patterns
Proven solutions to recurring design problems. Factory, Singleton, and Builder are the three patterns that appear in nearly every Java codebase — including Spring Boot.
Factory MethodSingletonBuilderwhen to use each
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Module 7
Unit Testing (JUnit)
Write tests that actually prove your code works. JUnit 5, Mockito, and Test-Driven Development — the skills that separate "it works on my machine" from a codebase teams can trust.
JUnit 5 assertionsmockingparameterized testsTDD