273. Complementing a conditional HttpHandler with another handler

Let’s assume that we want to choose between two HttpHandler instances based on a condition. For instance, for all GET requests, we want to use the following well-known HttpHandler:

HttpHandler fileHandler = SimpleFileServer.createFileHandler(
  Path.of("./docs").toAbsolutePath()); 

For all other requests, we want to use an HttpHandler that always returns the same resource (for instance, the text No data available). Defining a HttpHandler that always returns the same code and resource (so, a canned response) can be done via the HttpHandlers.of(int statusCode, Headers headers, String body) method as in the following example:

HttpHandler complementHandler = HttpHandlers.of(200,   
  Headers.of("Content-Type", "text/plain"), 
    "No data available");

In addition, the HttpHandler class exposes a method that can decide between two HttpHandler instances based...