# Package org.apache.tomcat.util.collections

- Class Summary
  Class | Description
  --- | ---
  CaseInsensitiveKeyMap<V> | A Map implementation that uses case-insensitive (using `Locale.ENGLISH`) strings as keys.
  ConcurrentCache<K,V> |
  ManagedConcurrentWeakHashMap<K,V> | Concurrent hash map that holds its keys via weak references.
  SynchronizedQueue<T> | This is intended as a (mostly) GC-free alternative to `ConcurrentLinkedQueue` when the requirement is to create an unbounded queue with no requirement to shrink the queue.
  SynchronizedStack<T> | This is intended as a (mostly) GC-free alternative to `ConcurrentLinkedQueue` when the requirement is to create a pool of re-usable objects with no requirement to shrink the pool.

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