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   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================== */
        

package org.apache.poi.poifs.dev;

import java.util.Iterator;

/**
 * Interface for a drill-down viewable object. Such an object has
 * content that may or may not be displayed, at the discretion of the
 * viewer. The content is returned to the viewer as an array or as an
 * Iterator, and the object provides a clue as to which technique the
 * viewer should use to get its content.
 *
 * A POIFSViewable object is also expected to provide a short
 * description of itself, that can be used by a viewer when the
 * viewable object is collapsed.
 *
 * @author Marc Johnson (mjohnson at apache dot org)
 */

public interface POIFSViewable
{

    /**
     * Get an array of objects, some of which may implement
     * POIFSViewable
     *
     * @return an array of Object; may not be null, but may be empty
     */

    public Object [] getViewableArray();
    
    /**
     * Get an Iterator of objects, some of which may implement
     * POIFSViewable
     *
     * @return an Iterator; may not be null, but may have an empty
     * back end store
     */
    public Iterator<Object> getViewableIterator();

    /**
     * Give viewers a hint as to whether to call getViewableArray or
     * getViewableIterator
     *
     * @return true if a viewer should call getViewableArray, false if
     *         a viewer should call getViewableIterator
     */

    public boolean preferArray();

    /**
     * Provides a short description of the object, to be used when a
     * POIFSViewable object has not provided its contents.
     *
     * @return short description
     */

    public String getShortDescription();
}   // end public interface POIFSViewable