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package javax.servlet.jsp.jstl.core;

/**
 * <p>Exposes the current status of
 * an iteration.  JSTL provides a mechanism for LoopTags to
 * return information about the current index of the iteration and
 * convenience methods to determine whether or not the current round is
 * either the first or last in the iteration.  It also lets authors
 * use the status object to obtain information about the iteration range,
 * step, and current object.</p>
 *
 * <p>Environments that require more status can extend this interface.</p>
 *
 * @author Shawn Bayern
 */

public interface LoopTagStatus {

    /**
     * Retrieves the current item in the iteration.  Behaves
     * idempotently; calling getCurrent() repeatedly should return the same
     * Object until the iteration is advanced.  (Specifically, calling
     * getCurrent() does <b>not</b> advance the iteration.)
     *
     * @return the current item as an object
     */
    public Object getCurrent();

    /**
     * Retrieves the index of the current round of the iteration.  If
     * iteration is being performed over a subset of an underlying
     * array, java.lang.Collection, or other type, the index returned
     * is absolute with respect to the underlying collection.  Indices
     * are 0-based.
     *
     * @return the 0-based index of the current round of the iteration
     */
    public int getIndex();

    /**
     * <p>Retrieves the "count" of the current round of the iteration.  The
     * count is a relative, 1-based sequence number identifying the
     * current "round" of iteration (in context with all rounds the
     * current iteration will perform).</p>
     *
     * <p>As an example, an iteration with begin = 5, end = 15, and step =
     * 5 produces the counts 1, 2, and 3 in that order.</p>
     *
     * @return the 1-based count of the current round of the iteration
     */
    public int getCount();

    /**
     * Returns information about whether the current round of the
     * iteration is the first one.  This current round may be the 'first'
     * even when getIndex() != 0, for 'index' refers to the absolute
     * index of the current 'item' in the context of its underlying
     * collection.  It is always that case that a true result from
     * isFirst() implies getCount() == 1.
     * 
     * @return <tt>true</tt> if the current round is the first in the
     * iteration, <tt>false</tt> otherwise.
     */
    public boolean isFirst();

    /**
     * Returns information about whether the current round of the
     * iteration is the last one.  As with isFirst(), subsetting is
     * taken into account.  isLast() doesn't necessarily refer to the
     * status of the underlying Iterator; it refers to whether or not
     * the current round will be the final round of iteration for the
     * tag associated with this LoopTagStatus.
     * 
     * @return <tt>true</tt> if the current round is the last in the
     * iteration, <tt>false</tt> otherwise.
     */
    public boolean isLast();

    /**
     * Returns the value of the 'begin' attribute for the associated tag,
     * or null if no 'begin' attribute was specified.
     *
     * @return the 'begin' value for the associated tag, or null
     * if no 'begin' attribute was specified
     */
    public Integer getBegin();

    /**
     * Returns the value of the 'end' attribute for the associated tag,
     * or null if no 'end' attribute was specified.
     *
     * @return the 'end' value for the associated tag, or null
     * if no 'end' attribute was specified
     */
    public Integer getEnd();

    /**
     * Returns the value of the 'step' attribute for the associated tag,
     * or null if no 'step' attribute was specified.
     *
     * @return the 'step' value for the associated tag, or null
     * if no 'step' attribute was specified
     */
    public Integer getStep();

}