Java 9 Zip End Header Not Found Exception

I am trying to batch download zip files from this URL using java - SRTM files and it requires a username/password to download and I am using the following java code and it gives me the following exception

java.util.zip.ZipException: zip END header not found
at java.util.zip.ZipFile$Source.zerror(java.base@9-internal/ZipFile.java:1210)
at java.util.zip.ZipFile$Source.findEND(java.base@9-internal/ZipFile.java:1119)
at java.util.zip.ZipFile$Source.initCEN(java.base@9-internal/ZipFile.java:1126)
at java.util.zip.ZipFile$Source.<init>(java.base@9-internal/ZipFile.java:963)
at java.util.zip.ZipFile$Source.get(java.base@9-internal/ZipFile.java:933)
at java.util.zip.ZipFile.<init>(java.base@9-internal/ZipFile.java:213)
at java.util.zip.ZipFile.<init>(java.base@9-internal/ZipFile.java:145)
at java.util.zip.ZipFile.<init>(java.base@9-internal/ZipFile.java:159)
at toposwapper.rules.ZipFileDownloadAction.execute(ZipFileDownloadAction.java:29)

This is my version of java

 java openjdk version "9-internal"
 OpenJDK Runtime Environment (build 9-internal+0-2016-04-14-195246.buildd.src)
 OpenJDK 64-Bit Server VM (build 9-internal+0-2016-04-14-195246.buildd.src, mixed mode)

This is the code that I am using to download -

    URL url1 = null;
    URLConnection conn = null;
    InputStream inputs = null;
    FileOutputStream out = null;
    try 
    {
        url1 = new URL(url);
        conn = url1.openConnection();
        conn.setDoInput(true);
        conn.setDoOutput(false);
        conn.setRequestProperty("file-name", output.getName());
        conn.setRequestProperty("content-type","application/zip");
        String userpass = this.username + ":" + this.password;
        String basicAuth = "Basic " + javax.xml.bind.DatatypeConverter.printBase64Binary(userpass.getBytes());
        conn.setRequestProperty("Authorization",basicAuth);
    } 
  catch (MalformedURLException ex) {
           Logger.getLogger(SrtmDownloadManager.class.getName()).log(Level.SEVERE, "", ex);
    throw new TopoSwapperException(ex.getMessage());
    }
  catch (IOException ioe)
    {
    Logger.getLogger(SrtmDownloadManager.class.getName()).log(Level.SEVERE, "", ioe);
    throw new TopoSwapperException(ioe.getMessage());
    }

    try 
      {
         inputs = conn.getInputStream();
         out = new FileOutputStream(output);
         byte[] b = new byte[1024];
         int count;
         while ((count = inputs.read(b)) > -1)
          {
            out.write(b,0,count);
           }
         out.flush();
         inputs.close();
         out.close();

      } 
    catch (FileNotFoundException ex) 
    {
        throw new TopoSwapperException(ex.getMessage());
    } 
    catch (IOException ex) 
    {
    Logger.getLogger(SrtmDownloadManager.class.getName()).log(Level.SEVERE, "", ex);
    throw new TopoSwapperException(ex.getMessage());
    }
finally
    {
        close(inputs);
        close(out);
    }

Can somebody help me why this fails ?

There are a few (already closed) bugs for Java 9 that mention this exception (eg. JDK-8170276, JDK-8172872). Since Java 9 is still in beta and you're using a version from over a year ago (2016-04-14 vs. July 2017 of the time of writing) you should upgrade to the newest Java 9 EA release or stick to Java 8 until a public release of Java 9.