java.net.JarURLConnection::getJarEntry() throws NullPointerException

Spec says: "Return the JAR entry object for this connection, if any. This method returns null if the JAR file URL corresponding to this connection points to a JAR file and not a JAR file entry."

However getJarEntry() throws NullPointerException instead of returning null in below scenario:

public static void main(String[] args) throws Exception {
        //please change below url accordingly
        URL url = new URL("jar:file:/D:/sample.jar!/");
        JarURLConnection jarURLConnection = new CustomJarURLConnection(url);
        /**
         * Spec says:
         *
         * Return the JAR entry object for this connection, if any. This
         * method returns null if the JAR file URL corresponding to this
         * connection points to a JAR file and not a JAR file entry.
         *
         * As "url" points to a JAR file and not a JAR file entry, hence getJarEntry() must return null.
         * However it throws null pointer exception.
         *
         **/
        JarEntry jarEntry = jarURLConnection.getJarEntry();
        System.out.println("This should be printed, however above line throws NullPointerException");
    }

    static class CustomJarURLConnection extends JarURLConnection {
        private URL pJarFileURL;
        protected CustomJarURLConnection(URL url) throws MalformedURLException {
            super(url);
            pJarFileURL = url;
        }

        @Override
        public JarFile getJarFile() throws IOException {
            return ((JarURLConnection)pJarFileURL.openConnection()).getJarFile();
        }

        @Override
        public void connect() throws IOException {}
    }
}