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Java Collections Overview

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This series focuses on real Java Collections interview questions. Typical topics include:

  • Core differences between List / Set / Map and their common implementations (ArrayList, LinkedList, HashSet, HashMap, etc.)
  • How HashMap works internally: array + linked list / red–black tree, resize mechanics, load factor, etc.
  • Concurrency design in ConcurrentHashMap: segment-style locking, CAS, and red–black trees.
  • Ordering and sorting: TreeMap / TreeSet and how they rely on Comparable / Comparator.
  • Thread-safe collections: when (and when not) to use Collections.synchronizedXxx, CopyOnWriteArrayList, and their trade-offs.

Later, under this “Java Collections” mini-category, we’ll expand with themed articles such as:

  • A deep dive into HashMap: differences between JDK 7 and JDK 8 implementations and common follow-up questions.
  • Performance comparisons and design questions: e.g. why choose ArrayList instead of LinkedList in most cases?
  • Pitfalls and best practices when using collections in concurrent scenarios.

For best results, read this together with the “Real-world interview questions” overview so you get both a macro structure and topic-level deep dives for your interview prep.