# Package org.zkoss.util

- Interface Summary
  Interface | Description
  --- | ---
  Cache<K,​V> | Represents a cache.
  Cleanups.Cleanup | The interface to implement for each cleanup.
  Converter<F,​T> | A converter used to convert a value to another.
  FilterMap.Filter<V> | Filters the given value (to evaluate when the value is retrieved).

- Class Summary
  Class | Description
  --- | ---
  ArraysX | Utilities for handling arrays.
  CacheMap<K,​V> | The cache map.
  CacheMap.Value<V> | The class to hold key/value.
  Checksums | Checksum relevant utilities.
  Cleanups | Utilities to clean up resources when the application is stopping.
  CollectionsX | The collection related utilities.
  CollectionsX.ArrayCollection<E> | An readonly collection on top of an array.
  CollectionsX.ArrayEnumeration<E> | An enumeration on top of an array.
  CollectionsX.ArrayIterator<E> | An iterator on top of an array.
  CollectionsX.ArrayList<E> | An readonly list on top of an array.
  CollectionsX.ArrayListIterator<E> |
  CollectionsX.CollectionEnumeration<E> | An enumeration on top of a collection or iterator.
  CollectionsX.EnumerationIterator<E> | An iterator that iterates thru an Enumeration.
  CollectionsX.OneCollection<E> | A collection that contains only one element.
  CollectionsX.OneEnumeration<E> | An enumeration that enumerates one element.
  CollectionsX.OneIterator<E> | An iterator that iterates one element.
  Dates | Utilities for java.util.Date
  DualCollection<T> | A combination of two collections into a collection.
  EmptyCacheMap<K,​V> | An empty cache map.
  FastReadArray<T> | An array of objects that are fast to read but a bit slower to add and remove.
  FastReadCache<K,​V> | A `CacheMap` that the possibility to have cache hit is much more than not.
  FilterMap<K,​V> | A map that allows the value to be evaluated before returning (so called filtering).
  IdentityComparator<T> | The comparator uses == and System.identifyHashCode to compare two objects.
  IdentityHashSet<T> | Like java.util.InternalHashMap, it uses == and System.identityHashCode for doing HashSet.
  Locales | The locale relevant utilities.
  Maps | Utilities for process Map.
  Maps.SerializableEntry<K,​V> | A serializable implement of Map.Entry
  MultiCache<K,​V> | A `CacheMap` that uses multiple instanceof `CacheMap` to speed up the performance.
  NotableLinkedList<E> | Linked list implementation of the `List` interface that provides the callback methods such as `NotableLinkedList.onAdd(E, E)`, `NotableLinkedList.onSet(E, E)` and `NotableLinkedList.onRemove(E)`.
  Pair<X,​Y> | A pair of keys.
  TimeZones | Utilities to access time-zone.
  URLs | Utility class for URL operations.
  Utils | Generic utilities.
  WaitLock | A simple lock used to implement load-on-demand mechanism.

- Exception Summary
  Exception | Description
  --- | ---
  IllegalSyntaxException | Represents a syntax error.