java 解密PDF格式文件

import java.io.FileOutputStream;
import com.lowagie.text.pdf.PdfEncryptor;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfStamper;
import com.lowagie.text.pdf.PdfWriter;
public class MainClass {
  public static void main(String[] args) throws Exception {
    PdfEncryptor
        .encrypt(new PdfReader("1.pdf"), new FileOutputStream("Encrypted2.pdf"),
            "Hello".getBytes(), "World".getBytes(), PdfWriter.AllowDegradedPrinting,
            PdfWriter.STRENGTH128BITS);
    // decrypt the file
    PdfReader reader = new PdfReader("Encrypted2.pdf", "World".getBytes());
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("Decrypted1.pdf"));
    stamper.close();
    getEncryptionInformation("1.pdf", null);
    getEncryptionInformation("Encrypted2.pdf", "World");
    getEncryptionInformation("Decrypted1.pdf", "World");
  }
  public static void getEncryptionInformation(String filename, String ownerpassword)
      throws Exception {
    PdfReader reader;
    if (ownerpassword == null)
      reader = new PdfReader(filename);
    else
      reader = new PdfReader(filename, ownerpassword.getBytes());
    System.out.println