Class StringIntHashMap

java.lang.Object
org.jibx.runtime.impl.StringIntHashMap

public class StringIntHashMap extends Object
Hash map using String values as keys mapped to primitive int values. This implementation is unsynchronized in order to provide the best possible performance for typical usage scenarios, so explicit synchronization must be implemented by a wrapper class or directly by the application in cases where instances are modified in a multithreaded environment. The map implementation is not very efficient when resizing, but works well when the size of the map is known in advance.
Version:
1.1
Author:
Dennis M. Sosnoski
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected static final double
    Default fill fraction allowed before growing table.
    static final int
    Default value returned when key not found in table.
    protected int
    Size of array used for keys.
    protected int
    Number of entries present in table.
    protected int
    Entries allowed before growing table.
    protected final double
    Fill fraction allowed for this hash table.
    protected int
    Offset added (modulo table size) to slot number on collision.
    protected String[]
    Array of key table slots.
    protected int
    Value returned when key not found in table.
    protected int[]
    Array of value table slots.
    protected static final int
    Minimum size used for hash table.
  • Constructor Summary

    Constructors
    Constructor
    Description
    Default constructor.
    StringIntHashMap(int count)
    Constructor with only size supplied.
    StringIntHashMap(int count, double fill)
    Constructor with size and fill fraction specified.
    StringIntHashMap(int count, double fill, int miss)
    Constructor with full specification.
    Copy (clone) constructor.
  • Method Summary

    Modifier and Type
    Method
    Description
    int
    add(String key, int value)
    Add an entry to the table.
    private int
    assignSlot(String key, int value)
    Assign slot for entry.
    Construct a copy of the table.
    final boolean
    Check if an entry is present in the table.
    private final int
    freeSlot(int slot)
    Find free slot number for entry.
    final int
    get(String key)
    Find an entry in the table.
    protected void
    internalRemove(int slot)
    Internal remove pair from the table.
    private boolean
    reinsert(int slot)
    Reinsert an entry into the hash map.
    int
    Remove an entry from the table.
    private void
    restructure(String[] keys, int[] values)
    Restructure the table.
    private int
    Standard find key in table.
    private final int
    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

    equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • DEFAULT_NOT_FOUND

      public static final int DEFAULT_NOT_FOUND
      Default value returned when key not found in table.
      See Also:
    • DEFAULT_FILL

      protected static final double DEFAULT_FILL
      Default fill fraction allowed before growing table.
      See Also:
    • MINIMUM_SIZE

      protected static final int MINIMUM_SIZE
      Minimum size used for hash table.
      See Also:
    • m_fillFraction

      protected final double m_fillFraction
      Fill fraction allowed for this hash table.
    • m_entryCount

      protected int m_entryCount
      Number of entries present in table.
    • m_entryLimit

      protected int m_entryLimit
      Entries allowed before growing table.
    • m_arraySize

      protected int m_arraySize
      Size of array used for keys.
    • m_hitOffset

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

      protected String[] m_keyTable
      Array of key table slots.
    • m_valueTable

      protected int[] m_valueTable
      Array of value table slots.
    • m_notFoundValue

      protected int m_notFoundValue
      Value returned when key not found in table.
  • Constructor Details

    • StringIntHashMap

      public StringIntHashMap(int count, double fill, int miss)
      Constructor with full specification.
      Parameters:
      count - number of values to assume in initial sizing of table
      fill - fraction full allowed for table before growing
      miss - value returned when key not found in table
    • StringIntHashMap

      public StringIntHashMap(int count, double fill)
      Constructor with size and fill fraction specified. Uses default hash technique and value returned when key not found in table.
      Parameters:
      count - number of values to assume in initial sizing of table
      fill - fraction full allowed for table before growing
    • StringIntHashMap

      public StringIntHashMap(int count)
      Constructor with only size supplied. Uses default hash technique and values for fill fraction and value returned when key not found in table.
      Parameters:
      count - number of values to assume in initial sizing of table
    • StringIntHashMap

      public StringIntHashMap()
      Default constructor.
    • StringIntHashMap

      public StringIntHashMap(StringIntHashMap base)
      Copy (clone) constructor.
      Parameters:
      base - instance being copied
  • 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(Object key)
      Standard base slot computation for a key.
      Parameters:
      key - key value to be computed
      Returns:
      base slot for key
    • standardFind

      private int standardFind(Object key)
      Standard find key in table. This method may be used directly for key lookup using either the hashCode() method defined for the key objects or the System.identityHashCode() method, and either the equals() method defined for the key objects or the == operator, 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 - 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)
    • reinsert

      private boolean reinsert(int slot)
      Reinsert an entry into the hash map. This is used when the table is being directly modified, and does not adjust the count present or check the table capacity.
      Parameters:
      slot - position of entry to be reinserted into hash map
      Returns:
      true if the slot number used by the entry has has changed, false if not
    • internalRemove

      protected void internalRemove(int slot)
      Internal remove pair from the table. Removes the pair from the table by setting the key entry to null and adjusting the count present, then chains through the table to reinsert any other pairs which may have collided with the removed pair. If the associated value is an object reference, it should be set to null before this method is called.
      Parameters:
      slot - index number of pair to be removed
    • restructure

      private void restructure(String[] keys, int[] values)
      Restructure the table. This is used when the table is increasing or decreasing in size, and works directly with the old table representation arrays. It inserts pairs from the old arrays directly into the table without adjusting the count present or checking the table size.
      Parameters:
      keys - array of keys
      values - array of values
    • assignSlot

      private int assignSlot(String key, int value)
      Assign slot for entry. Starts at the slot found by the hashed key value. If this slot is already occupied, it steps the slot number and checks the resulting slot, repeating until an unused slot is found. This method does not check for duplicate keys, so it should only be used for internal reordering of the tables.
      Parameters:
      key - to be added to table
      value - associated value for key
      Returns:
      slot at which entry was added
    • add

      public int add(String key, int value)
      Add an entry to the table. If the key is already present in the table, this replaces the existing value associated with the key.
      Parameters:
      key - key to be added to table (non- null)
      value - associated value for key
      Returns:
      value previously associated with key, or reserved not found value if key not previously present in table
    • containsKey

      public final boolean containsKey(String key)
      Check if an entry is present in the table. This method is supplied to support the use of values matching the reserved not found value.
      Parameters:
      key - key for entry to be found
      Returns:
      true if key found in table, false if not
    • get

      public final int get(String key)
      Find an entry in the table.
      Parameters:
      key - key for entry to be returned
      Returns:
      value for key, or reserved not found value if key not found
    • remove

      public int remove(String key)
      Remove an entry from the table. If multiple entries are present with the same key value, only the first one found will be removed.
      Parameters:
      key - key to be removed from table
      Returns:
      value associated with removed key, or reserved not found value if key not found in table
    • clone

      public Object clone()
      Construct a copy of the table.
      Overrides:
      clone in class Object
      Returns:
      shallow copy of table