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Class calypso.util.HashtableBase
java.lang.Object | +----calypso.util.HashtableBase
Object subclass that implements a hash table.
abstract class HashtableBase
extends java.lang.Object
implements java.lang.Cloneable
{
// Fields 12
static final int A;
static final int DEFAULT;
static final int EMPTY;
static final int REMOVED;
int capacity;
int count;
Object[] elements;
int[] hashCodes;
int indexMask;
Object[] keys;
int shift;
int totalCount;
// Constructors 2
HashtableBase();
HashtableBase(int);
// Methods 19
public void clear();
public Object clone();
boolean containsElement(Object);
public int count();
public Enumeration elements();
public Vector elementsVector();
int getElementsArray(Object[]);
int getKeysArray(Object[]);
protected void grow();
private void grow(int);
int hash(Object);
public boolean isEmpty();
public Enumeration keys();
public Vector keysVector();
Object put(Object, Object);
Object removeKey(Object);
public int size();
int tableIndexFor(Object, int);
public String toString();
}
Fields
• A
static final int A
For the multiplicative hash, choose the golden ratio:A = ((sqrt(5) - 1) / 2) * (1 << 32)ala Knuth...
• EMPTY
static final int EMPTY
We use EMPTY and REMOVED as special markers in the table. If some poor object returns one of these two values as their hashCode, it is wacked to DEFAULT.
• REMOVED
static final int REMOVED
• DEFAULT
static final int DEFAULT
• count
int count
• totalCount
int totalCount
• shift
int shift
• capacity
int capacity
• indexMask
int indexMask
• hashCodes
int[] hashCodes
• keys
Object[] keys
• elements
Object[] elements
Constructors
• HashtableBase
HashtableBase()
Constructs an empty Hashtable. The Hashtable will grow on demand as more elements are added.
• HashtableBase
HashtableBase(int aInitialCapacity)
Constructs a Hashtable capable of holding at least initialCapacity elements before needing to grow.
Methods
• clone
public Object clone()
• count
public int count()
Returns the number of elements in the Hashtable.
• size
public int size()
Returns the number of elements in the Hashtable.
• isEmpty
public boolean isEmpty()
Returns true if there are no elements in the Hashtable.
• keys
public Enumeration keys()
Returns an Enumeration of the Hashtable's keys.
See Also: elements
• elements
public Enumeration elements()
Returns an Enumeration of the Hashtable's elements.
See Also: keys
• keysVector
public Vector keysVector()
Returns a Vector containing the Hashtable's keys.
• elementsVector
public Vector elementsVector()
Returns a Vector containing the Hashtable's elements.
• getKeysArray
int getKeysArray(Object[] aArray)
Returns an Object array containing the Hashtable's keys.
• getElementsArray
int getElementsArray(Object[] aArray)
Returns an Object array containing the Hashtable's elements.
• containsElement
boolean containsElement(Object aElement)
Returns true if the Hashtable contains the element. This method is slow -- O(n) -- because it must scan the table searching for the element.
• removeKey
Object removeKey(Object aKey)
Removes key and the element associated with it from the Hashtable. Returns the element associated with key, or null if key was not present.
• put
Object put(Object aKey, Object aElement)
Places the key/element pair in the Hashtable. Neither key nor element may be null. Returns the old element associated with key, or null if the key was not present.
• hash
int hash(Object aKey)
We preclude the hashCodes EMPTY and REMOVED because we use them to indicate empty and previously filled slots in the table. All the Hashtable code should go through here and not call hashCode() directly on the key.
• tableIndexFor
int tableIndexFor(Object aKey, int aHash)
Primitive method used internally to find slots in the table. If the key is present in the table, this method will return the index under which it is stored. If the key is not present, then this method will return the index under which it can be put. The caller must look at the hashCode at that index to differentiate between the two possibilities.
• grow
private void grow(int aCapacity)
Grows the table to accommodate at least capacity number of elements.
• grow
protected void grow()
Grows the table by a factor of 2 (or creates it if necessary). All the REMOVED markers go away and the elements are rehashed into the bigger table.
• clear
public void clear()
Removes all keys and elements from the Hashtable.
• toString
public String toString()
Returns a string serialization of the Hashtable using the Serializer.
- Overrides:
- toString in class Object
See Also: Serializer
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