The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
You might need to configure your web server to handle Java Network Launch Protocol (JNLP) files. If the web server is not set up properly, the Java Web Start application will not launch when you click on the link to the JNLP file.
Configure the web server so that files with the .jnlp extension are set to the application/x-java-jnlp-file MIME type.
The specific steps to set up the JNLP MIME type will vary depending on the web server. As an example, to configure an Apache web server, you should add the following line to the mime.types file.
application/x-java-jnlp-file JNLP
For other web servers, check the documentation for instructions on setting MIME types.