程序包 org.beetl.core.util

类 ArrayMap<K,V>

java.lang.Object
org.beetl.core.util.ArrayMap<K,V>
所有已实现的接口:
Map<K,V>
public final class ArrayMap<K,V> extends Object implements Map<K,V>
ArrayMap is a generic key->value mapping data structure that is designed to be more memory efficient than a traditional HashMap. It keeps its mappings in an array data structure -- an integer array of hash codes for each item, and an Object array of the key/value pairs. This allows it to avoid having to create an extra object for every entry put in to the map, and it also tries to control the growth of the size of these arrays more aggressively (since growing them only requires copying the entries in the array, not rebuilding a hash map).

Note that this implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.

Because this container is intended to better balance memory use, unlike most other standard Java containers it will shrink its array as items are removed from it. Currently you have no control over this shrinking -- if you set a capacity and then remove an item, it may reduce the capacity to better match the current size. In the future an explicit call to set the capacity should turn off this aggressive shrinking behavior.

  • 字段详细资料

    • EMPTY

      public static final ArrayMap EMPTY

  • 构造器详细资料

    • ArrayMap

      public ArrayMap()
      Create a new empty ArrayMap. The default capacity of an array map is 0, and will grow once items are added to it.

    • ArrayMap

      public ArrayMap(int capacity)
      Create a new ArrayMap with a given initial capacity.

    • ArrayMap

      public ArrayMap(int capacity, boolean identityHashCode)

    • ArrayMap

      public ArrayMap(ArrayMap<K,V> map)
      Create a new ArrayMap with the mappings from the given ArrayMap.

  • 方法详细资料

    • clear

      public void clear()
      Make the array map empty. All storage is released.
      指定者:
      clear 在接口中 Map<K,V>

    • erase

      public void erase()

    • ensureCapacity

      public void ensureCapacity(int minimumCapacity)
      Ensure the array map can hold at least minimumCapacity items.

    • containsKey

      public boolean containsKey(Object key)
      Check whether a key exists in the array.
      指定者:
      containsKey 在接口中 Map<K,V>
      参数:
      key - The key to search for.
      返回:
      Returns true if the key exists, else false.

    • indexOfKey

      public int indexOfKey(Object key)
      Returns the index of a key in the set.
      参数:
      key - The key to search for.
      返回:
      Returns the index of the key if it exists, else a negative integer.

    • indexOfValue

      public int indexOfValue(Object value)
      Returns an index for which valueAt(int) would return the specified value, or a negative number if no keys map to the specified value. Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them.

    • containsValue

      public boolean containsValue(Object value)
      Check whether a value exists in the array. This requires a linear search through the entire array.
      指定者:
      containsValue 在接口中 Map<K,V>
      参数:
      value - The value to search for.
      返回:
      Returns true if the value exists, else false.

    • get

      public V get(Object key)
      Retrieve a value from the array.
      指定者:
      get 在接口中 Map<K,V>
      参数:
      key - The key of the value to retrieve.
      返回:
      Returns the value associated with the given key, or null if there is no such key.

    • keyAt

      public K keyAt(int index)
      Return the key at the given index in the array.
      参数:
      index - The desired index, must be between 0 and size()-1.
      返回:
      Returns the key stored at the given index.

    • valueAt

      public V valueAt(int index)
      Return the value at the given index in the array.
      参数:
      index - The desired index, must be between 0 and size()-1.
      返回:
      Returns the value stored at the given index.

    • setValueAt

      public V setValueAt(int index, V value)
      Set the value at a given index in the array.
      参数:
      index - The desired index, must be between 0 and size()-1.
      value - The new value to store at this index.
      返回:
      Returns the previous value at the given index.

    • isEmpty

      public boolean isEmpty()
      Return true if the array map contains no items.
      指定者:
      isEmpty 在接口中 Map<K,V>

    • put

      public V put(K key, V value)
      Add a new value to the array map.
      指定者:
      put 在接口中 Map<K,V>
      参数:
      key - The key under which to store the value. If this key already exists in the array, its value will be replaced.
      value - The value to store for the given key.
      返回:
      Returns the old value that was stored for the given key, or null if there was no such key.

    • append

      public void append(K key, V value)
      Special fast path for appending items to the end of the array without validation. The array must already be large enough to contain the item.

    • validate

      public void validate()
      The use of the append(K, V) function can result in invalid array maps, in particular an array map where the same key appears multiple times. This function verifies that the array map is valid, throwing IllegalArgumentException if a problem is found. The main use for this method is validating an array map after unpacking from an IPC, to protect against malicious callers.

    • putAll

      public void putAll(ArrayMap<? extends K,? extends V> array)
      Perform a put(Object, Object) of all key/value pairs in array
      参数:
      array - The array whose contents are to be retrieved.

    • remove

      public V remove(Object key)
      Remove an existing key from the array map.
      指定者:
      remove 在接口中 Map<K,V>
      参数:
      key - The key of the mapping to remove.
      返回:
      Returns the value that was stored under the key, or null if there was no such key.

    • removeAt

      public V removeAt(int index)
      Remove the key/value mapping at the given index.
      参数:
      index - The desired index, must be between 0 and size()-1.
      返回:
      Returns the value that was stored at this index.

    • size

      public int size()
      Return the number of items in this array map.
      指定者:
      size 在接口中 Map<K,V>

    • equals

      public boolean equals(Object object)

      This implementation returns false if the object is not a map, or if the maps have different sizes. Otherwise, for each key in this map, values of both maps are compared. If the values for any key are not equal, the method returns false, otherwise it returns true.

      指定者:
      equals 在接口中 Map<K,V>
      覆盖:
      equals 在类中 Object

    • hashCode

      public int hashCode()
      指定者:
      hashCode 在接口中 Map<K,V>
      覆盖:
      hashCode 在类中 Object

    • toString

      public String toString()

      This implementation composes a string by iterating over its mappings. If this map contains itself as a key or a value, the string "(this Map)" will appear in its place.

      覆盖:
      toString 在类中 Object

    • containsAll

      public boolean containsAll(Collection<?> collection)
      Determine if the array map contains all of the keys in the given collection.
      参数:
      collection - The collection whose contents are to be checked against.
      返回:
      Returns true if this array map contains a key for every entry in collection, else returns false.

    • putAll

      public void putAll(Map<? extends K,? extends V> map)
      Perform a put(Object, Object) of all key/value pairs in map
      指定者:
      putAll 在接口中 Map<K,V>
      参数:
      map - The map whose contents are to be retrieved.

    • removeAll

      public boolean removeAll(Collection<?> collection)
      Remove all keys in the array map that exist in the given collection.
      参数:
      collection - The collection whose contents are to be used to remove keys.
      返回:
      Returns true if any keys were removed from the array map, else false.

    • retainAll

      public boolean retainAll(Collection<?> collection)
      Remove all keys in the array map that do not exist in the given collection.
      参数:
      collection - The collection whose contents are to be used to determine which keys to keep.
      返回:
      Returns true if any keys were removed from the array map, else false.

    • entrySet

      public Set<Map.Entry<K,V>> entrySet()
      Return a Set for iterating over and interacting with all mappings in the array map.

      Note: this is a very inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.

      Note:

      the semantics of this Set are subtly different than that of a HashMap: most important, the Map.Entry object returned by its iterator is a single object that exists for the entire iterator, so you can not hold on to it after calling Iterator.next.

      指定者:
      entrySet 在接口中 Map<K,V>

    • keySet

      public Set<K> keySet()
      Return a Set for iterating over and interacting with all keys in the array map.

      Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.

      指定者:
      keySet 在接口中 Map<K,V>

    • values

      public Collection<V> values()
      Return a Collection for iterating over and interacting with all values in the array map.

      Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.

      指定者:
      values 在接口中 Map<K,V>