Modern open source projects frequently lack documentation and so does hbase regarding its REST API. Even though REST is covered in the official hbase reference book the guidelines are not complete as I’ll show in the listings below. A second source that you might have come across is a set of three blog posts by Cloudera which is quite good and much more detailled than the official hbase guidelines – but it still does not fully cover then traps you might run into when implementing a java client.
I’d like to show three examples, two for a put and one for a get request. All further operations like delete or post should then be easy to implement once you know how to send requests to the REST server.