# FreeXReference.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.pdfparser.xref;

    import org.apache.pdfbox.cos.COSObjectKey;
    import org.apache.pdfbox.pdfparser.PDFXRefStream;

    /**
     * A class representing a free reference in a PDF's crossreference stream ({@link PDFXRefStream}).
     *
     * @author Christian Appl
     */
    public class FreeXReference extends AbstractXReference
    {

        public static final FreeXReference NULL_ENTRY = //
                new FreeXReference(new COSObjectKey(0, 65535), 0);
        private final COSObjectKey key;
        private final long nextFreeObject;

        /**
         * Sets the given {@link COSObjectKey} as a free reference in a PDF's crossreference stream ({@link PDFXRefStream}).
         *
         * @param key The key, that shall be set as the free reference of the document.
         * @param nextFreeObject The object number of the next free object.
         */
        public FreeXReference(COSObjectKey key, long nextFreeObject)
        {
            super(XReferenceType.FREE);
            this.key = key;
            this.nextFreeObject = nextFreeObject;
        }

        /**
         * Returns the {@link COSObjectKey} of the object, that is described by this crossreference stream entry.
         *
         * @return The {@link COSObjectKey} of the object, that is described by this crossreference stream entry.
         */
        @Override
        public COSObjectKey getReferencedKey()
        {
            return key;
        }

        /**
         * Returns the value for the second column of the crossreference stream entry. (This is the object number of the set
         * next free {@link COSObjectKey} - for entries of this type.)
         *
         * @return The value for the second column of the crossreference stream entry.
         */
        @Override
        public long getSecondColumnValue()
        {
            return nextFreeObject;
        }

        /**
         * Returns the value for the third column of the crossreference stream entry. (This is the generation number of the
         * set next free {@link COSObjectKey} - for entries of this type.)
         *
         * @return The value for the third column of the crossreference stream entry.
         */
        @Override
        public long getThirdColumnValue()
        {
            return getReferencedKey().getGeneration();
        }

        /**
         * Returns a string representation of this crossreference stream entry.
         *
         * @return A string representation of this crossreference stream entry.
         */
        @Override
        public String toString()
        {
            return "FreeReference{" + "key=" + key + ", nextFreeObject=" + nextFreeObject + ", type="
                    + getType().getNumericValue() + " }";
        }
    }