How to replace the deprecated URL constructors in Java 20?

All URL constructors are deprecated in Java 20. I replaced new URL(protocol, host, file) by new URI(protocol, host, file, null).toURL() as I have no query and no fragment but I don't know what to do with the others:

/home/gouessej/Documents/programmation/java/workspace/Ardor3D/ardor3d-core/src/main/java/com/ardor3d/util/UrlUtils.java:40: warning: [deprecation] URL(String) in URL has been deprecated
        return new URL(new URL(url), relativeLoc);
                       ^
/home/gouessej/Documents/programmation/java/workspace/Ardor3D/ardor3d-core/src/main/java/com/ardor3d/util/UrlUtils.java:40: warning: [deprecation] URL(URL,String) in URL has been deprecated
        return new URL(new URL(url), relativeLoc);
               ^
/home/gouessej/Documents/programmation/java/workspace/Ardor3D/ardor3d-core/src/main/java/com/ardor3d/util/resource/SimpleResourceLocator.java:94: warning: [deprecation] URL(URL,String) in URL has been deprecated
            final URL rVal = new URL(_baseDir.toURL(), spec);
                             ^
/home/gouessej/Documents/programmation/java/workspace/Ardor3D/ardor3d-audio/src/main/java/com/ardor3d/audio/FilenameURL.java:125: warning: [deprecation] URL(String) in URL has been deprecated
                    url = new URL( filename );

Would simply new URI(filename).toURL()do the job in the last case?

When I compare the wording in the Java documentation, I understand that an URI scheme means more or less a URL protocol, an URI host is an URL host and an URL file matches with a URI path and an optional URI query. What are the exact equivalent of new URL(spec) and new URL(context, spec)?

I prepared some suggested changes but it doesn't work, an IllegalArgumentException is thrown.

Solution

tl;dr

To construct a URL, use URI::toURL.
To construct a relative URL, first create the URI using the context URI and then call URI::resolve with the URI you wish to make relative.
To construct a file: based URL, (1) call Path::toURI, (2) then URI::toURL.

Ex: URI uri = Paths.get( "/Users/your_user_name/example.txt" ).toUri() ;

Details

Understand that:

java.net.URL is an ancient class, dating from Java 1. That class does not encode or decode any URL components according to the RFC 2396 escaping mechanism.
java.net.URI class came later, in Java 4.

Read this note from the Java team, Oracle: Quality Outreach Heads-up - JDK 20: Deprecate URL Public Constructors. To quote:

JDK 20 will deprecate all public constructors of java.net.URL. … To construct a URL, the URI::toURL alternative should instead be preferred. To construct a file: based URL, Path::toURI should be used prior to URI::toURL.

And see the note on constructor deprecation within the Javadoc of URL class.

See also the issue-tracker page, JDK-8294241 Deprecate URL public constructors.

Example: File path URI

For working with files in modern Java, use NIO.2 features.

The Paths class can produce a Path object.
From there, ask that Path to produce a URI.

Path path = Paths.get( "/Users/your_user_name/example.txt" ) ;
URI uri = path.toUri () ;

uri.toString() = file:///Users/your_user_name/example.txt

Going the other direction:

Path path = Paths.get( uri ) ;