import java.io.IOException;
import java.io.RandomAccessFile;

public class ZipTest {
    public static void main(String[] args) {
      String file = null;
      /* use the first parameter as the input zip file */
      if (args.length > 0)
          file = args[0];

      RandomAccessFile zipFile = null;
      try {
          zipFile = new RandomAccessFile(file, "r");

          long fileSize = zipFile.length();
          /* find the magic number in a reverse manner */
          for (long i = 1 ; fileSize - i >= 0; ++i) {
              zipFile.seek(fileSize - i);
              byte b = zipFile.readByte();
              if (b == 0x06) {
                  zipFile.seek(fileSize - i - 3);
                  /* check for magic "0x06054b50" in little endian */
                  byte[] key = new byte[4];
                  zipFile.readFully(key);
                  if (key[0] != 0x50 || key[1] != 0x4b || key[2] != 0x05) {
                      continue;
                  }
                  /* get the file comment size */
                  byte[] tmp = new byte[18];
                  zipFile.readFully(tmp);
                  int commentSize = (tmp[16] & 0xff) | ((tmp[17] & 0xff) >> 8);
                  if (commentSize > 0) {
                      byte[] comment = new byte[commentSize];
                      zipFile.readFully(comment);
                      System.out.println("comment: " + new String(comment));
                  }
                  break;
              }
          }
      } catch(Exception ex) {
          ex.printStackTrace();
      } finally {
          if (zipFile != null) {
              try {
                  zipFile.close();
              } catch (IOException ex) {
              }
          }
      }
    }
}