hashtable.java

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	Entry newMap[] = new Entry[newCapacity];

	modCount++;
	threshold = (int)(newCapacity * loadFactor);
	table = newMap;

	for (int i = oldCapacity ; i-- > 0 ;) {
	    for (Entry old = oldMap[i] ; old != null ; ) {
		Entry e = old;
		old = old.next;

		int index = (e.hash & 0x7FFFFFFF) % newCapacity;
		e.next = newMap[index];
		newMap[index] = e;
	    }
	}
    }

    /**
     * Maps the specified <code>key</code> to the specified 
     * <code>value</code> in this hashtable. Neither the key nor the 
     * value can be <code>null</code>. <p>
     *
     * The value can be retrieved by calling the <code>get</code> method 
     * with a key that is equal to the original key. 
     *
     * @param      key     the hashtable key.
     * @param      value   the value.
     * @return     the previous value of the specified key in this hashtable,
     *             or <code>null</code> if it did not have one.
     * @exception  NullPointerException  if the key or value is
     *               <code>null</code>.
     * @see     Object#equals(Object)
     * @see     #get(Object)
     */
    public synchronized Object put(Object key, Object value) {
	// Make sure the value is not null
	if (value == null) {
	    throw new NullPointerException();
	}

	// Makes sure the key is not already in the hashtable.
	Entry tab[] = table;
	int hash = key.hashCode();
	int index = (hash & 0x7FFFFFFF) % tab.length;
	for (Entry e = tab[index] ; e != null ; e = e.next) {
	    if ((e.hash == hash) && e.key.equals(key)) {
		Object old = e.value;
		e.value = value;
		return old;
	    }
	}

	modCount++;
	if (count >= threshold) {
	    // Rehash the table if the threshold is exceeded
	    rehash();

            tab = table;
            index = (hash & 0x7FFFFFFF) % tab.length;
	} 

	// Creates the new entry.
	Entry e = new Entry(hash, key, value, tab[index]);
	tab[index] = e;
	count++;
	return null;
    }

    /**
     * Removes the key (and its corresponding value) from this 
     * hashtable. This method does nothing if the key is not in the hashtable.
     *
     * @param   key   the key that needs to be removed.
     * @return  the value to which the key had been mapped in this hashtable,
     *          or <code>null</code> if the key did not have a mapping.
     * @throws  NullPointerException  if the key is <code>null</code>.
     */
    public synchronized Object remove(Object key) {
	Entry tab[] = table;
	int hash = key.hashCode();
	int index = (hash & 0x7FFFFFFF) % tab.length;
	for (Entry e = tab[index], prev = null ; e != null ; prev = e, e = e.next) {
	    if ((e.hash == hash) && e.key.equals(key)) {
		modCount++;
		if (prev != null) {
		    prev.next = e.next;
		} else {
		    tab[index] = e.next;
		}
		count--;
		Object oldValue = e.value;
		e.value = null;
		return oldValue;
	    }
	}
	return null;
    }

    /**
     * Copies all of the mappings from the specified Map to this Hashtable
     * These mappings will replace any mappings that this Hashtable had for any
     * of the keys currently in the specified Map. 
     *
     * @param t Mappings to be stored in this map.
     * @throws NullPointerException if the specified map is null.
     * @since 1.2
     */
    public synchronized void putAll(Map t) {
	Iterator i = t.entrySet().iterator();
	while (i.hasNext()) {
	    Map.Entry e = (Map.Entry) i.next();
	    put(e.getKey(), e.getValue());
	}
    }

    /**
     * Clears this hashtable so that it contains no keys. 
     */
    public synchronized void clear() {
	Entry tab[] = table;
	modCount++;
	for (int index = tab.length; --index >= 0; )
	    tab[index] = null;
	count = 0;
    }

    /**
     * Creates a shallow copy of this hashtable. All the structure of the 
     * hashtable itself is copied, but the keys and values are not cloned. 
     * This is a relatively expensive operation.
     *
     * @return  a clone of the hashtable.
     */
    public synchronized Object clone() {
	try { 
	    Hashtable t = (Hashtable)super.clone();
	    t.table = new Entry[table.length];
	    for (int i = table.length ; i-- > 0 ; ) {
		t.table[i] = (table[i] != null) 
		    ? (Entry)table[i].clone() : null;
	    }
	    t.keySet = null;
	    t.entrySet = null;
            t.values = null;
	    t.modCount = 0;
	    return t;
	} catch (CloneNotSupportedException e) { 
	    // this shouldn't happen, since we are Cloneable
	    throw new InternalError();
	}
    }

    /**
     * Returns a string representation of this <tt>Hashtable</tt> object 
     * in the form of a set of entries, enclosed in braces and separated 
     * by the ASCII characters "<tt>,&nbsp;</tt>" (comma and space). Each 
     * entry is rendered as the key, an equals sign <tt>=</tt>, and the 
     * associated element, where the <tt>toString</tt> method is used to 
     * convert the key and element to strings. <p>Overrides to 
     * <tt>toString</tt> method of <tt>Object</tt>.
     *
     * @return  a string representation of this hashtable.
     */
    public synchronized String toString() {
	int max = size() - 1;
	StringBuffer buf = new StringBuffer();
	Iterator it = entrySet().iterator();

	buf.append("{");
	for (int i = 0; i <= max; i++) {
	    Map.Entry e = (Map.Entry) (it.next());
            Object key = e.getKey();
            Object value = e.getValue();
            buf.append((key   == this ? "(this Map)" : key) + "=" + 
                       (value == this ? "(this Map)" : value));

	    if (i < max)
		buf.append(", ");
	}
	buf.append("}");
	return buf.toString();
    }


    private Enumeration getEnumeration(int type) {
	if (count == 0) {
	    return emptyEnumerator;
	} else {
	    return new Enumerator(type, false);
	}
    }

    private Iterator getIterator(int type) {
	if (count == 0) {
	    return emptyIterator;
	} else {
	    return new Enumerator(type, true);
	}
    }

    // Views

    /**
     * Each of these fields are initialized to contain an instance of the
     * appropriate view the first time this view is requested.  The views are
     * stateless, so there's no reason to create more than one of each.
     */
    private transient volatile Set keySet = null;
    private transient volatile Set entrySet = null;
    private transient volatile Collection values = null;

    /**
     * Returns a Set view of the keys contained in this Hashtable.  The Set
     * is backed by the Hashtable, so changes to the Hashtable are reflected
     * in the Set, and vice-versa.  The Set supports element removal
     * (which removes the corresponding entry from the Hashtable), but not
     * element addition.
     *
     * @return a set view of the keys contained in this map.
     * @since 1.2
     */
    public Set keySet() {
	if (keySet == null)
	    keySet = Collections.synchronizedSet(new KeySet(), this);
	return keySet;
    }

    private class KeySet extends AbstractSet {
        public Iterator iterator() {
	    return getIterator(KEYS);
        }
        public int size() {
            return count;
        }
        public boolean contains(Object o) {
            return containsKey(o);
        }
        public boolean remove(Object o) {
            return Hashtable.this.remove(o) != null;
        }
        public void clear() {
            Hashtable.this.clear();
        }
    }

    /**
     * Returns a Set view of the entries contained in this Hashtable.
     * Each element in this collection is a Map.Entry.  The Set is
     * backed by the Hashtable, so changes to the Hashtable are reflected in
     * the Set, and vice-versa.  The Set supports element removal
     * (which removes the corresponding entry from the Hashtable),
     * but not element addition.
     *
     * @return a set view of the mappings contained in this map.
     * @see   Map.Entry
     * @since 1.2
     */
    public Set entrySet() {
	if (entrySet==null)
	    entrySet = Collections.synchronizedSet(new EntrySet(), this);
	return entrySet;
    }

    private class EntrySet extends AbstractSet {
        public Iterator iterator() {
	    return getIterator(ENTRIES);
        }

        public boolean contains(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry entry = (Map.Entry)o;
            Object key = entry.getKey();
            Entry tab[] = table;
            int hash = key.hashCode();
            int index = (hash & 0x7FFFFFFF) % tab.length;

            for (Entry e = tab[index]; e != null; e = e.next)
                if (e.hash==hash && e.equals(entry))
                    return true;
            return false;
        }

        public boolean remove(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry entry = (Map.Entry)o;
            Object key = entry.getKey();
            Entry tab[] = table;
            int hash = key.hashCode();
            int index = (hash & 0x7FFFFFFF) % tab.length;

            for (Entry e = tab[index], prev = null; e != null;
                 prev = e, e = e.next) {
                if (e.hash==hash && e.equals(entry)) {
                    modCount++;
                    if (prev != null)
                        prev.next = e.next;
                    else
                        tab[index] = e.next;

                    count--;
                    e.value = null;
                    return true;
                }
            }
            return false;
        }

        public int size() {
            return count;
        }

        public void clear() {
            Hashtable.this.clear();
        }
    }

    /**
     * Returns a Collection view of the values contained in this Hashtable.
     * The Collection is backed by the Hashtable, so changes to the Hashtable
     * are reflected in the Collection, and vice-versa.  The Collection
     * supports element removal (which removes the corresponding entry from
     * the Hashtable), but not element addition.
     *
     * @return a collection view of the values contained in this map.
     * @since 1.2
     */
    public Collection values() {
	if (values==null)
	    values = Collections.synchronizedCollection(new ValueCollection(),
                                                        this);
        return values;
    }

    private class ValueCollection extends AbstractCollection {
        public Iterator iterator() {
	    return getIterator(VALUES);
        }
        public int size() {
            return count;
        }
        public boolean contains(Object o) {
            return containsValue(o);
        }
        public void clear() {
            Hashtable.this.clear();
        }
    }

    // Comparison and hashing

    /**