Class SimpleHashtable

  • All Implemented Interfaces:
    java.util.Enumeration

    final class SimpleHashtable
    extends java.lang.Object
    implements java.util.Enumeration
    This class implements a special purpose hashtable. It works like a normal java.util.Hashtable except that:

    1. Keys to "get" are strings which are known to be interned, so that "==" is used instead of "String.equals". (Interning could be document-relative instead of global.)

    2. It's not synchronized, since it's to be used only by one thread at a time.

    3. The keys () enumerator allocates no memory, with live updates to the data disallowed.

    4. It's got fewer bells and whistles: fixed threshold and load factor, no JDK 1.2 collection support, only keys can be enumerated, things can't be removed, simpler inheritance; more.

    The overall result is that it's less expensive to use these in performance-critical locations, in terms both of CPU and memory, than java.util.Hashtable instances. In this package it makes a significant difference when normalizing attributes, which is done for each start-element construct.

    Version:
    $Revision: 1.2 $
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      private static class  SimpleHashtable.Entry
      Hashtable collision list.
    • Constructor Summary

      Constructors 
      Constructor Description
      SimpleHashtable()
      Constructs a new, empty hashtable with a default capacity.
      SimpleHashtable​(int initialCapacity)
      Constructs a new, empty hashtable with the specified initial capacity.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()  
      java.lang.Object get​(java.lang.String key)
      Returns the value to which the specified key is mapped in this hashtable.
      java.lang.Object getNonInterned​(java.lang.String key)
      Returns the value to which the specified key is mapped in this hashtable ...
      boolean hasMoreElements()
      Used to view this as an enumeration; returns true if there are more keys to be enumerated.
      java.util.Enumeration keys()
      Returns an enumeration of the keys in this hashtable.
      java.lang.Object nextElement()
      Used to view this as an enumeration; returns the next key in the enumeration.
      java.lang.Object put​(java.lang.Object key, java.lang.Object value)
      Maps the specified key to the specified value in this hashtable.
      private void rehash()
      Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently.
      int size()
      Returns the number of keys in this hashtable.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
      • Methods inherited from interface java.util.Enumeration

        asIterator
    • Constructor Detail

      • SimpleHashtable

        public SimpleHashtable​(int initialCapacity)
        Constructs a new, empty hashtable with the specified initial capacity.
        Parameters:
        initialCapacity - the initial capacity of the hashtable.
      • SimpleHashtable

        public SimpleHashtable()
        Constructs a new, empty hashtable with a default capacity.
    • Method Detail

      • clear

        public void clear()
      • size

        public int size()
        Returns the number of keys in this hashtable.
        Returns:
        the number of keys in this hashtable.
      • keys

        public java.util.Enumeration keys()
        Returns an enumeration of the keys in this hashtable.
        Returns:
        an enumeration of the keys in this hashtable.
        See Also:
        Enumeration
      • hasMoreElements

        public boolean hasMoreElements()
        Used to view this as an enumeration; returns true if there are more keys to be enumerated.
        Specified by:
        hasMoreElements in interface java.util.Enumeration
      • nextElement

        public java.lang.Object nextElement()
        Used to view this as an enumeration; returns the next key in the enumeration.
        Specified by:
        nextElement in interface java.util.Enumeration
      • get

        public java.lang.Object get​(java.lang.String key)
        Returns the value to which the specified key is mapped in this hashtable.
      • getNonInterned

        public java.lang.Object getNonInterned​(java.lang.String key)
        Returns the value to which the specified key is mapped in this hashtable ... the key isn't necessarily interned, though.
      • rehash

        private void rehash()
        Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently. This method is called automatically when the number of keys in the hashtable exceeds this hashtable's capacity and load factor.
      • put

        public java.lang.Object put​(java.lang.Object key,
                                    java.lang.Object value)
        Maps the specified key to the specified value in this hashtable. Neither the key nor the value can be null.

        The value can be retrieved by calling the get method with a key that is equal to the original key.