Package org.jibx.util

Class StringSizedSet

java.lang.Object
org.jibx.util.StringSizedSet
public class StringSizedSet extends Object
Fixed size hash set of String values.
Author:
Dennis M. Sosnoski

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final double
    DEFAULT_FILL_FRACTION
    Default fill fraction for sizing of tables.
    protected final int
    m_arraySize
    Size of array used for keys.
    protected final int
    m_hitOffset
    Offset added (modulo table size) to slot number on collision.
    protected final String[]
    m_keyTable
    Array of key table slots.

  • Constructor Summary

    Constructors
    Constructor
    Description
    StringSizedSet(int count)
    Constructor with only value count specified.
    StringSizedSet(int count, double fill)
    Constructor with full specification.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(String key)
    Add a key to the set.
    void
    clear()
    Set the table to the empty state.
    final boolean
    contains(String key)
    Check if an entry is present in the table.
    private final int
    freeSlot(int slot)
    Find free slot number for entry.
    private int
    standardFind(String key)
    Standard find key in table.
    private final int
    standardSlot(String key)
    Standard base slot computation for a key.
    private final int
    stepSlot(int slot)
    Step the slot number for an entry.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • DEFAULT_FILL_FRACTION

      public static final double DEFAULT_FILL_FRACTION
      Default fill fraction for sizing of tables.
      See Also:

    • m_arraySize

      protected final int m_arraySize
      Size of array used for keys.

    • m_keyTable

      protected final String[] m_keyTable
      Array of key table slots.

    • m_hitOffset

      protected final int m_hitOffset
      Offset added (modulo table size) to slot number on collision.

  • Constructor Details

    • StringSizedSet

      public StringSizedSet(int count, double fill)
      Constructor with full specification.
      Parameters:
      count - number of values to assume in sizing of table
      fill - fraction fill for table (maximum of 0.7, to prevent excessive collisions)

    • StringSizedSet

      public StringSizedSet(int count)
      Constructor with only value count specified. Uses default fill fraction and miss value.
      Parameters:
      count - number of values to assume in initial sizing of table

  • Method Details

    • stepSlot

      private final int stepSlot(int slot)
      Step the slot number for an entry. Adds the collision offset (modulo the table size) to the slot number.
      Parameters:
      slot - slot number to be stepped
      Returns:
      stepped slot number

    • freeSlot

      private final int freeSlot(int slot)
      Find free slot number for entry. Starts at the slot based directly on the hashed key value. If this slot is already occupied, it adds the collision offset (modulo the table size) to the slot number and checks that slot, repeating until an unused slot is found.
      Parameters:
      slot - initial slot computed from key
      Returns:
      slot at which entry was added

    • standardSlot

      private final int standardSlot(String key)
      Standard base slot computation for a key. This method may be used directly for key lookup using either the hashCode() method defined for the key objects or the System.identityHashCode() method, as selected by the hash technique constructor parameter. To implement a hash class based on some other methods of hashing and/or equality testing, define a separate method in the subclass with a different name and use that method instead. This avoids the overhead caused by overrides of a very heavily used method.
      Parameters:
      key - key value to be computed
      Returns:
      base slot for key

    • standardFind

      private int standardFind(String key)
      Standard find key in table. This uses equals comparisons for the key values.
      Parameters:
      key - to be found in table
      Returns:
      index of matching key, or -index-1 of slot to be used for inserting key in table if not already present (always negative)

    • add

      public boolean add(String key)
      Add a key to the set. If the key is already present in the set, this does nothing.
      Parameters:
      key - key to be added to table (non-null)
      Returns:
      true if added, false if already present value if key not previously present in table

    • contains

      public final boolean contains(String key)
      Check if an entry is present in the table.
      Parameters:
      key - key to be found
      Returns:
      true if key found in table, false if not

    • clear

      public void clear()
      Set the table to the empty state.