# PDAppearanceEntry.java

    /*
     * 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.pdfbox.pdmodel.interactive.annotation;

    import java.util.HashMap;
    import java.util.Map;
    import org.apache.pdfbox.cos.COSDictionary;
    import org.apache.pdfbox.cos.COSName;
    import org.apache.pdfbox.cos.COSStream;
    import org.apache.pdfbox.pdmodel.common.COSDictionaryMap;
    import org.apache.pdfbox.pdmodel.common.COSObjectable;

    /**
     * An entry in an appearance dictionary. May contain either a single appearance stream or an appearance subdictionary.
     *
     * @author John Hewson
     */
    public class PDAppearanceEntry implements COSObjectable
    {
        private COSDictionary entry;

        private PDAppearanceEntry()
        {
        }

        /**
         * Constructor for reading.
         *
         * @param entry
         */
        public PDAppearanceEntry(COSDictionary entry)
        {
            this.entry = entry;
        }

        @Override
        public COSDictionary getCOSObject()
        {
            return entry;
        }

        /**
         * Returns true if this entry is an appearance subdictionary.
         */
        public boolean isSubDictionary()
        {
            return !(this.entry instanceof COSStream);
        }

        /**
         * Returns true if this entry is an appearance stream.
         */
        public boolean isStream()
        {
            return this.entry instanceof COSStream;
        }

        /**
         * Returns the entry as an appearance stream.
         *
         * @throws IllegalStateException if this entry is not an appearance stream
         */
        public PDAppearanceStream getAppearanceStream()
        {
            if (!isStream())
            {
                throw new IllegalStateException("This entry is not an appearance stream");
            }
            return new PDAppearanceStream((COSStream) entry);
        }

        /**
         * Returns the entry as an appearance subdictionary.
         *
         * @throws IllegalStateException if this entry is not an appearance subdictionary
         */
        public Map<COSName, PDAppearanceStream> getSubDictionary()
        {
            if (!isSubDictionary())
            {
                throw new IllegalStateException("This entry is not an appearance subdictionary");
            }

            COSDictionary dict = entry;
            Map<COSName, PDAppearanceStream> map = new HashMap<>();

            for (COSName name : dict.keySet())
            {
                COSStream stream = dict.getCOSStream(name);
                // the file from PDFBOX-1599 contains /null as its entry, so we skip non-stream entries
                if (stream != null)
                {
                    map.put(name, new PDAppearanceStream(stream));
                }
            }
            return new COSDictionaryMap<>(map, dict);
        }
    }