Why URI constructor allows missing protocol (while URL does not)?

Question

Why does URI allow missing protocol (while URL does not)?

In wikipedia Scheme (and even Path) seem to be obligatory components of an URI:

The URI generic syntax consists of a hierarchical sequence of five components:[8]

URI = scheme:[//authority]path[?query][#fragment]

Or missing protocol defaults to something (like http)? I found nothing like this in the docs.

new URI("my.html");        // 1
new URI("xabc:my.html");   // 2
new URL("my.html");        // 3      
new URL("xabc:my.html");   // 4

Concerning "obligatory" path - OK, there is oblique URI. But why missing protocol is allowed (it shall be present even for obligue URI which is required to be absolute)

I could understand that relative URL/URI don't require protocol (<img src="/images/pic.png">), but URL gives run-time java.net.MalformedURLException: no protocol in this case either (while URI don't).

Show code that throw MalformedURLException exception

Ori Marko
– Ori Marko

2019-01-07 09:57:25 +00:00
Commented Jan 7, 2019 at 9:57 — Ori Marko
– Ori Marko, Commented Jan 7, 2019 at 9:57

Ori Marko · Accepted Answer · 2019-01-07 10:29:30Z

1

Your relative path must be wrong, Java's URI supports empty scheme for relative URI:

relative URI, that is, a URI that does not specify a scheme. Some examples of hierarchical URIs are:
docs/guide/collections/designfaq.html#28

Scheme is optional:

[scheme:]scheme-specific-part[#fragment]

Similar with URL, e.g.:

URL url = new URL("/guidelines.txt");

edited Jan 7, 2019 at 10:29

answered Jan 7, 2019 at 9:52

Ori Marko

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