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org.apache.commons.collections
public class: FastHashMap [javadoc | source]
java.lang.Object
   java.util.AbstractMap
      java.util.HashMap
         org.apache.commons.collections.FastHashMap

All Implemented Interfaces:
    Map, Serializable, Cloneable

Direct Known Subclasses:
    DelegateFastHashMap

A customized implementation of java.util.HashMap designed to operate in a multithreaded environment where the large majority of method calls are read-only, instead of structural changes. When operating in "fast" mode, read calls are non-synchronized and write calls perform the following steps:

When first created, objects of this class default to "slow" mode, where all accesses of any type are synchronized but no cloning takes place. This is appropriate for initially populating the collection, followed by a switch to "fast" mode (by calling setFast(true)) after initialization is complete.

NOTE: If you are creating and accessing a HashMap only within a single thread, you should use java.util.HashMap directly (with no synchronization), for maximum performance.

NOTE: This class is not cross-platform. Using it may cause unexpected failures on some architectures. It suffers from the same problems as the double-checked locking idiom. In particular, the instruction that clones the internal collection and the instruction that sets the internal reference to the clone can be executed or perceived out-of-order. This means that any read operation might fail unexpectedly, as it may be reading the state of the internal collection before the internal collection is fully formed. For more information on the double-checked locking idiom, see the Double-Checked Locking Idiom Is Broken Declaration.

Field Summary
protected  HashMap map    The underlying map we are managing. 
protected  boolean fast    Are we currently operating in "fast" mode? 
Fields inherited from java.util.HashMap:
DEFAULT_INITIAL_CAPACITY,  MAXIMUM_CAPACITY,  DEFAULT_LOAD_FACTOR,  table,  size,  threshold,  loadFactor,  modCount
Fields inherited from java.util.AbstractMap:
keySet,  values
Constructor:
 public FastHashMap() 
 public FastHashMap(int capacity) 
 public FastHashMap(Map map) 
    Construct a new map with the same mappings as the specified map.
    Parameters:
    map - the map whose mappings are to be copied
 public FastHashMap(int capacity,
    float factor) 
Method from org.apache.commons.collections.FastHashMap Summary:
clear,   clone,   containsKey,   containsValue,   entrySet,   equals,   get,   getFast,   hashCode,   isEmpty,   keySet,   put,   putAll,   remove,   setFast,   size,   values
Methods from java.util.HashMap:
addEntry,   capacity,   clear,   clone,   containsKey,   containsValue,   createEntry,   entrySet,   get,   getEntry,   hash,   indexFor,   init,   isEmpty,   keySet,   loadFactor,   newEntryIterator,   newKeyIterator,   newValueIterator,   put,   putAll,   remove,   removeEntryForKey,   removeMapping,   resize,   size,   transfer,   values
Methods from java.util.AbstractMap:
access$000,   clear,   clone,   containsKey,   containsValue,   entrySet,   equals,   get,   hashCode,   isEmpty,   keySet,   put,   putAll,   remove,   size,   toString,   values
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.apache.commons.collections.FastHashMap Detail:
 public  void clear() 
    Remove all mappings from this map.
 public Object clone() 
    Return a shallow copy of this FastHashMap instance. The keys and values themselves are not copied.
 public boolean containsKey(Object key) 
    Return true if this map contains a mapping for the specified key.
 public boolean containsValue(Object value) 
    Return true if this map contains one or more keys mapping to the specified value.
 public Set entrySet() 
    Return a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry.
 public boolean equals(Object o) 
    Compare the specified object with this list for equality. This implementation uses exactly the code that is used to define the list equals function in the documentation for the Map.equals method.
 public Object get(Object key) 
    Return the value to which this map maps the specified key. Returns null if the map contains no mapping for this key, or if there is a mapping with a value of null. Use the containsKey() method to disambiguate these cases.
 public boolean getFast() 
    Returns true if this map is operating in fast mode.
 public int hashCode() 
    Return the hash code value for this map. This implementation uses exactly the code that is used to define the list hash function in the documentation for the Map.hashCode method.
 public boolean isEmpty() 
    Return true if this map contains no mappings.
 public Set keySet() 
    Return a set view of the keys contained in this map.
 public Object put(Object key,
    Object value) 
    Associate the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced and returned.
 public  void putAll(Map in) 
    Copy all of the mappings from the specified map to this one, replacing any mappings with the same keys.
 public Object remove(Object key) 
    Remove any mapping for this key, and return any previously mapped value.
 public  void setFast(boolean fast) 
    Sets whether this map is operating in fast mode.
 public int size() 
    Return the number of key-value mappings in this map.
 public Collection values() 
    Return a collection view of the values contained in this map.