HashtableK,V

Hashtable<K,V>

java.util

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Java 1.0

cloneable serializable collection

This class implements a hashtable data structure, which maps key objects to value objects and allows the efficient lookup of the value associated with a given key. In Java 1.2 and later Hashtable has been modified to impement the Map interface. The HashMap class is typically preferred over this one, although the synchronized methods of this class are useful in multi-threaded applications. (But see java.util.concurrent.ConcurrentHashMap .) In Java 5.0 this class has been made generic along with the Map interface. The type variable K represents the type of the hashtable keys and the type variable V represents the type of the hashtable values.

put( ) associates a value with a key in a Hashtable . get( ) retrieves a value for a specified key. remove( ) deletes a key/value association. keys( ) and elements( ) return Enumeration objects that allow you to iterate through the complete set of keys and values stored in the table. Objects used as keys in a Hashtable must have valid equals( ) and hashCode( ) methods (the versions inherited from Object are okay). null is not legal as a key or value in a Hashtable .

Figure 16-26. java.util.Hashtable<K,V>

 public class  Hashtable<K,V>  extends Dictionary<K,V> implements Map<K,V>,          Cloneable, Serializable {  // Public Constructors  public  Hashtable  ( );  1.2  public  Hashtable  (Map<? extends K,? extends V>  t  );        public  Hashtable  (int  initialCapacity  );        public  Hashtable  (int  initialCapacity  , float  loadFactor  );  // Public Instance Methods  public void  clear  ( );  Implements:  Map synchronized      public boolean  contains  (Object  value  );  synchronized  public boolean  containsKey  (Object  key  );  Implements:  Map synchronized      public V  get  (Object  key  );  Implements:  Map synchronized      public boolean  isEmpty  ( );  Implements:  Map synchronized default:true      public V  put  (K  key  , V  value  );  Implements:  Map synchronized      public V  remove  (Object  key  );  Implements:  Map synchronized      public int  size  ( );  Implements:  Map synchronized  // Methods Implementing Map  public void  clear  ( );  synchronized  public boolean  containsKey  (Object  key  );  synchronized   1.2  public boolean  containsValue  (Object  value  );  1.2  public Set<Map.Entry<K,V>>  entrySet  ( );  1.2  public boolean  equals  (Object  o  );  synchronized  public V  get  (Object  key  );  synchronized   1.2  public int  hashCode  ( );  synchronized  public boolean  isEmpty  ( );  synchronized  default:true  1.2  public Set<K>  keySet  ( );        public V  put  (K  key  , V  value  );  synchronized   1.2  public void  putAll  (Map<? extends K,? extends V>  t  );  synchronized  public V  remove  (Object  key  );  synchronized  public int  size  ( );  synchronized   1.2  public Collection<V>  values  ( );  // Public Methods Overriding Dictionary  public Enumeration<V>  elements  ( );  synchronized  public Enumeration<K>  keys  ( );  synchronized   // Public Methods Overriding Object  public Object  clone  ( );  synchronized  public String  toString  ( );  synchronized   // Protected Instance Methods  protected void  rehash  ( );   } 

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