Java Roadmap for Backend and Placements

Core Java, collections, concurrency and the Spring ecosystem that most campus and service-company roles ask about.

8 milestones · ~126 hours total

1. 1

   Syntax and the JVM

   ~8h

   Install the JDK, compile and run, types, operators, control flow, and what the JVM, JRE and JIT actually do.

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2. 2

   Object-oriented design

   ~16h

   Classes, interfaces, abstract classes, inheritance vs composition, encapsulation and the SOLID basics.

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3. 3

   Collections and generics

   ~14h

   List, Set, Map, Queue implementations, their complexity, equals/hashCode and generics.

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4. 4

   Exceptions, I/O and streams

   ~12h

   Checked vs unchecked exceptions, try-with-resources, file I/O, lambdas and the Stream API.

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5. 5

   Concurrency

   ~16h

   Threads, synchronization, ExecutorService, CompletableFuture and common pitfalls like deadlock and race conditions.

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6. 6

   Build tools and testing

   ~10h

   Maven or Gradle, JUnit 5, Mockito and writing tests before you refactor.

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7. 7

   Spring Boot and databases

   ~30h

   REST controllers, dependency injection, JPA/Hibernate, transactions and connecting to PostgreSQL or MySQL.

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8. 8

   Interview preparation

   ~20h

   Collections internals, memory model and garbage collection questions, plus data-structure problems solved in Java.

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