gnu.trove.THashIterator Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of trove4j Show documentation
The Trove library provides high speed regular and primitive collections for Java.
There is a newer version: 3.0.3
///////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2001, Eric D. Friedman All Rights Reserved.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
///////////////////////////////////////////////////////////////////////////////

package gnu.trove;

import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Implements all iterator functions for the hashed object set.
 * Subclasses may override objectAtIndex to vary the object
 * returned by calls to next() (e.g. for values, and Map.Entry
 * objects).
 *
 *  Note that iteration is fastest if you forego the calls to
 * hasNext in favor of checking the size of the structure
 * yourself and then call next() that many times:
 *
 * 
 * Iterator i = collection.iterator();
 * for (int size = collection.size(); size-- > 0;) {
 *   Object o = i.next();
 * }
 * 
 *
 * You may, of course, use the hasNext(), next() idiom too if
 * you aren't in a performance critical spot.
 *
 */
abstract class THashIterator extends TIterator implements Iterator {
    private final TObjectHash _object_hash;

    /**
     * Create an instance of THashIterator over the values of the TObjectHash
     */
    public THashIterator(TObjectHash hash) {
        super(hash);
        _object_hash = hash;
    }
    
    /**
     * Moves the iterator to the next Object and returns it.
     *
     * @return an Object value
     * @exception ConcurrentModificationException if the structure
     * was changed using a method that isn't on this iterator.
     * @exception NoSuchElementException if this is called on an
     * exhausted iterator.
     */
    public V next() {
        moveToNextIndex();
        return objectAtIndex(_index);
    }

    /**
     * Returns the index of the next value in the data structure
     * or a negative value if the iterator is exhausted.
     *
     * @return an int value
     * @exception ConcurrentModificationException if the underlying
     * collection's size has been modified since the iterator was
     * created.
     */
    protected final int nextIndex() {
        if (_expectedSize != _hash.size()) {
            throw new ConcurrentModificationException();
        }

        Object[] set = _object_hash._set;
        int i = _index;
        while (i-- > 0 && (set[i] == TObjectHash.FREE || set[i] == TObjectHash.REMOVED)) ;
        return i;
    }

    /**
     * Returns the object at the specified index.  Subclasses should
     * implement this to return the appropriate object for the given
     * index.
     *
     * @param index the index of the value to return.
     * @return an Object value
     */
    abstract protected V objectAtIndex(int index);
} // THashIterator