PDF concatination with merging the bookmarks

PdfConcatWithBookmark.java

package com.blogspot.catin136.pdfconcatwithbookmark;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.pdf.BadPdfFormatException;
import com.lowagie.text.pdf.PdfCopy;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfSmartCopy;
import com.lowagie.text.pdf.SimpleBookmark;

public class PdfConcatWithBookmark {
    private Document doc = null;
    private PdfCopy copy = null;
    private List<HashMap<String,Object>> bookmark = null;
    private int numOfPage = 0;
    
    public PdfConcatWithBookmark(OutputStream output) throws DocumentException {
	doc = new Document();
	copy = new PdfSmartCopy(doc, output);
	bookmark = new ArrayList<HashMap<String,Object>>();
	
	copy.setFullCompression();
	doc.open();
    }
    
    public PdfConcatWithBookmark(String output) throws FileNotFoundException, DocumentException {
	this(new FileOutputStream(output));
    }
    
    public void addPdfFile(String path) throws BadPdfFormatException, IOException {
	PdfReader reader = new PdfReader(path);
	List<HashMap<String,Object>> fileBookmark = SimpleBookmark.getBookmark(reader);
	
	SimpleBookmark.shiftPageNumbers(fileBookmark, numOfPage, null);
	bookmark.addAll(fileBookmark);
	
	int filePageCount = reader.getNumberOfPages();
	for (int page = 1; page <= filePageCount; page++) {
	    copy.addPage(copy.getImportedPage(reader, page));
	    numOfPage++;
	}
	
	copy.freeReader(reader);
	reader.close();
    }
    
    public void close() {
	copy.setOutlines(bookmark);
	doc.close();
    }

    public static void main(String[] args) throws DocumentException, IOException {
	if (args.length >= 2) {
	    PdfConcatWithBookmark concat = null;
	    try {
		concat = new PdfConcatWithBookmark(args[args.length - 1]);
		for (int i = 0; i < args.length - 1; i++) {
		    concat.addPdfFile(args[i]);
		}
	    } finally {
		if (concat != null) {
		    concat.close();
		}
	    }
	} else {
	    System.out.println("Usage: java -cp ... "
		    + PdfConcatWithBookmark.class.getCanonicalName()
		    + " input1.pdf input2.pdf ... output.pdf");
	    System.exit(1);
	}
    }

}