Subversion Repositories aduna

/*
 * Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2008.
 *
 * Licensed under the Aduna BSD-style license.
 */

package info.aduna.iteration;

/**
 * An Iteration that skips the first <tt>offset</tt> elements from an
 * underlying Iteration.
 */
public class OffsetIteration<E, X extends Exception> extends FilterIteration<E, X> {

    /*-----------*
     * Variables *
     *-----------*/

    /**
     * The offset (0-based) of the first element to return.
     */
    private final long offset;

    /**
     * The number of elements that have been dropped so far.
     */
    private long droppedResults;

    /*--------------*
     * Constructors *
     *--------------*/

    /**
     * Creates a new OffsetIteration.
     * 
     * @param iter
     *        The underlying Iteration, must not be <tt>null</tt>.
     * @param offset
     *        The number of elements to skip, must be larger than or equal to 0.
     */
    public OffsetIteration(Iteration<? extends E, X> iter, long offset) {
        super(iter);

        assert offset >= 0;

        this.offset = offset;
        this.droppedResults = 0;
    }

    /*---------*
     * Methods *
     *---------*/

    /**
     * Returns <tt>false</tt> for the first OFFSET objects.
     */
    protected boolean accept(E object) {
        if (droppedResults < offset) {
            droppedResults++;
            return false;
        }
        else {
            return true;
        }
    }
}