Java provides several Map implementations in the java.util package, each with unique characteristics and use cases. Here's a concise overview:

1. HashMap 📦

  • Unordered key-value pairs
  • Fast get and put operations (average O(1))
  • Allows null keys and values
  • Commonly used for general-purpose storage
HashMap

2. TreeMap 📊

  • Sorted by natural ordering or custom comparator
  • Slower than HashMap for large datasets (O(log n))
  • Maintains keys in ascending order
  • Ideal for sorted traversal or range queries
TreeMap

3. LinkedHashMap 🔗

  • Retains insertion order (extends HashMap)
  • Useful for caching or maintaining access order
  • Slightly slower than HashMap due to extra linkage

4. ConcurrentHashMap 🧠

  • Thread-safe for multithreaded environments
  • Supports concurrent reads and writes
  • Ideal for high-concurrency applications
ConcurrentHashMap

5. Hashtable 📁

  • Legacy class (synchronized)
  • Does not allow null keys or values
  • Slower than HashMap due to synchronization

For deeper insights into Java collections, explore our guide on Java Collections Framework. 🚀