chainedhashtableiterator.java

关于迭代器、构造器

package structure;
import java.util.Iterator;

/**
 * A traversal of all the elements as they appear in a chained hashtable.
 * No order is guaranteed.  This iterator is not publically accessable
 * and is used to implement ChainedHashtable's key and value iterators.
 * This iteration returns objects that are instances of {@link Association}.
 * <P>
 * Typical use:
 * <P>
 * <pre>
 *      ChainedHashtable h = new ChainedHashtable();
 *      // ...hashtable gets built up...
 *      Iterator hi = new {@link #ChainedHashtableIterator(List[]) ChainedHashtableIterator(h.data)};
 *      while (hi.{@link #hasNext() hasNext()})
 *      {
 *          System.out.println(ai.{@link #next() next()});
 *      }
 * </pre> 
 *
 * @version $Id: ChainedHashtableIterator.java,v 4.0 2000/12/28 21:50:39 bailey Exp bailey $
 * @author, 2001 duane a. bailey
 */
class ChainedHashtableIterator extends AbstractIterator
{
    /**
     * The list of values within the table.
     */
    protected List data;
    /**
     * The iterator over the elements of the list.
     */
    protected Iterator elements;

    /**
     * Construct an iterator over a chained hashtable.
     *
     * @post constructs a new hash table iterator
     * @param table The array of lists to be traversed.
     */
    public ChainedHashtableIterator(List[] table)
    {
	int i;
	int capacity = table.length;
	data = new SinglyLinkedList();
	for (i = 0; i < capacity; i++) {
	    if (table[i] != null) {
		Iterator els = table[i].iterator();
		while (els.hasNext())
		{
		    data.addFirst(els.next());
		}
	    }
	}
	elements = data.iterator();
    }

    /**
     * Resets the iterator to point to the beginning of the chained table.
     *
     * @post resets iterator to beginning of hash table
     */
    public void reset()
    {
	((AbstractIterator)elements).reset();
    }

    /**
     * Returns true iff there are unconsidered elements within the table.
     *
     * @post returns true if there are unvisited elements
     * 
     * @return True iff there are elements yet to be considered within table.
     */
    public boolean hasNext()
    {
	return elements.hasNext();
    }

    /**
     * Returns current value and increments iterator.
     *
     * @pre hasNext()
     * @post returns current element, increments iterator
     * 
     * @return The current value, before incrementing.
     */
    public Object next()
    {
	return elements.next();
    }

    /**
     * Get current value of iterator.
     *
     * @post returns current element
     * 
     * @return The current value.
     */
    public Object get()
    {
	return ((AbstractIterator)elements).get();
    }
}