Top Tricky Java Interview Questions and Answers | Java Interview Questions and Answers | Code Decode

by Code Decode

🧠 Main Topics Covered

  1. Java Collections and Enhancements

    • Latest enhancements in HashMap (Java 8)
    • Introduction to the Optional class
  2. Java 8 Functional Programming

    • Differences between map and flatMap
  3. Design Patterns

    • Differences between Factory and Abstract Factory design patterns
  4. Spring Framework

    • Different scopes in Spring
    • Differences between Spring and Spring Boot
    • Introduction to Spring AOP (Aspect-Oriented Programming)
  5. Garbage Collection

    • Explanation of Metaspace and its differences from PermGen
  6. Exception Handling

    • Explanation of multi-catch blocks in Java
  7. Hibernate

    • Benefits of Criteria API in Hibernate
    • Types of cascade operations supported by JPA
  8. Microservices

    • Definition and advantages of microservices architecture

✨ Key Takeaways

  • HashMap EnhancementsJava 8 improved HashMap performance by replacing linked lists with balanced trees, reducing worst-case time complexity from O(n) to O(log n).
  • Optional ClassA utility to prevent null pointer exceptions by providing a container that may or may not hold a value.
  • Functional Programmingmap is for one-to-one transformations, while flatMap is for one-to-many transformations and flattening collections.
  • Design PatternsFactory creates objects, while Abstract Factory creates factories that return objects.
  • Spring ScopesSingleton and Prototype are the most common scopes, with Request, Session, and Global Session being less frequently used.
  • Spring BootSimplifies Spring framework usage by reducing boilerplate code and managing dependencies.
  • AOPSegregates cross-cutting concerns from business logic, enhancing modularity.
  • Garbage CollectionMetaspace allows dynamic memory allocation for class metadata, unlike the fixed-size PermGen.
  • Exception HandlingMulti-catch blocks allow handling multiple exceptions in a single catch statement.
  • HibernateCriteria API allows dynamic query creation without hard-coded SQL, and JPA supports various cascade operations for entity relationships.
  • MicroservicesPromotes independent service deployment, resilience, scalability, and faster time to market.

🧠 Lessons Learned

  • Understanding the enhancements in Java collections and the functional programming paradigm is crucial for modern Java development.
  • Familiarity with design patterns and frameworks like Spring and Hibernate is essential for building scalable applications.
  • Knowledge of microservices architecture is increasingly important for developing robust and maintainable software systems.

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