如何实用Java实现合并、拆分PDF文档

import com.spire.pdf.*;
import java.io.*;

public class Merge2 {
	public static void main(String[] args) throws Exception {
    
		String outputFile = "output/mergeFilesByStream.pdf";
    FileInputStream stream1 = new FileInputStream(new File("sample1.pdf"));
    FileInputStream stream2 = new FileInputStream(new File("sample2.pdf"));
    FileInputStream stream3 = new FileInputStream(new File("sample3.pdf"));
    //加载PDF示例文档
    InputStream[] streams = new FileInputStream[]{stream1, stream2, stream3};

    //合并PDF文档
    PdfDocumentBase doc = PdfDocument.mergeFiles(streams);

    //保存文档
    doc.save(outputFile);
    doc.close();
  }
}

import com.spire.pdf.*;

public class SplitPDF1 {
	public static void main(String[] args)
	{
	//加载需要拆分的PDF文档
  PdfDocument doc = new PdfDocument();
  doc.loadFromFile("test.pdf");

  //调用方法split()将PDF文档按每一页拆分为单独的文档
  doc.split("output/splitDocument-{0}.pdf", 0);
  doc.close();
	}
}

import com.spire.pdf.*; 
import com.spire.pdf.graphics.PdfMargins; 
 
import java.awt.geom.Point2D; 
 
public class SplitPDF2 { 
  public static void main(String[] args) 
  { 
 
    //加载需要拆分的PDF文档 
    PdfDocument doc = new PdfDocument(); 
    doc.loadFromFile("test.pdf"); 
 
    //新建第1个PDF文档1 
    PdfDocument newpdf1 = new PdfDocument(); 
    PdfPageBase page; 
 
    //将原PDF文档的第1、2页拆分，并保存到newpdf1 
    for(int i = 0;i<2;i++) 
    { 
      page = newpdf1.getPages().add(doc.getPages().get(i).getSize(), new PdfMargins(0)); 
      doc.getPages().get(i).createTemplate().draw(page, new Point2D.Float(0,0)); 
    } 
    newpdf1.saveToFile("split/result1.pdf"); 
 
    //新建第2个PDF文档 
    PdfDocument newpdf2 = new PdfDocument(); 
 
    //将原PDF文档的第3、4页拆分，并保存到newpdf2 
    for(int i = 2;i<4;i++) 
    { 
      page = newpdf2.getPages().add(doc.getPages().get(i).getSize(), new PdfMargins(0)); 
      doc.getPages().get(i).createTemplate().draw(page, new Point2D.Float(0,0)); 
    } 
    newpdf2.saveToFile("split/result2.pdf"); 
  } 
}