As written here: Java Client Roadmap Update
During the past five years, most browser vendors have withdrawn
support for plugins such as Flash, Silverlight, and Java in their
products. Supporting Java Applets in browsers was only possible as
long as browser vendors were committed to supporting standards based
plugins. By late 2015, many browser vendors had either removed or
announced timelines for the removal of standards-based plugin support,
while some introduced proprietary browser-specific extension APIs.
Consequently:
- Existing Applet support in Java SE 8 will continue through March 2019, after which it may be removed at any time.
- Oracle announced in January 2016 that Applets would be deprecated in Java SE 9, and removed from Java SE 11 (18.9).
The Alternative:
You will need to find potential Third Party Replacement. Import explicitly (eg using maven)