Java
The enterprise workhorse, learned properly.
Java in depth: language fundamentals, OOP done right, collections and generics, streams, exceptions, the JVM, concurrency and build tooling - the Java that runs banks and Fortune 500 backends.
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- 1
Language Fundamentals
Comfortable with Java's syntax and compile-time discipline.
2 weeks0/4Primitives vs reference types, autoboxing and String immutability - the static-typing ground rules.
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Conditionals, loops, switch expressions, method overloading and static vs instance.
Fixed-size arrays, StringBuilder for concatenation-heavy code, and common pitfalls.
javac/java, your IDE and reading Javadoc - the daily toolchain.
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- 2
Object-Oriented Java
Model domains the way Java intends.
2–3 weeks0/4Constructors, access modifiers, getters with intent - objects as guarded state plus behaviour.
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extends, overriding, dynamic dispatch - and why composition usually beats inheritance.
Contracts, default methods and programming to interfaces - the backbone of testable design.
Immutable data carriers and typed constants - modern Java's answer to boilerplate.
- 3
Collections & Generics
Choose and use data structures like a professional.
2 weeks0/4ArrayList vs LinkedList, HashSet vs TreeSet, HashMap internals - the trade-offs interviews probe.
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Type parameters, bounded wildcards and erasure - type-safe containers without fear.
The contracts that make collections behave - and the bugs when they're broken.
Functional pipelines: filter/map/collect, Optional and method references.
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- 4
Exceptions & IO
Fail well; read and write the world.
1–2 weeks0/3Checked vs unchecked, try-with-resources and designing error paths that callers can handle.
java.nio.file, readers/writers and resources on the classpath.
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java.time: Instant, LocalDate, ZonedDateTime - the API that finally got dates right.
- 5
JVM & Concurrency
Understand the platform under your code.
2–3 weeks0/4Heap vs stack, garbage collection basics - enough to read an OutOfMemoryError calmly.
Runnable, thread pools, synchronized and race conditions - concurrency as a first-class topic.
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Maven/Gradle: dependencies, lifecycle and packaging a runnable jar.
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Assertions, lifecycle annotations and test naming - the safety net for refactoring.
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- 6
Ship & Prove
Job-ready evidence.
1–2 weeks0/2Controllers, dependency injection and a REST endpoint - the framework most Java jobs assume.
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Take the OneRoadmap Java certification - verified proof for the resume line.
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