API for parsing path strings

[Jonathan Gibbons]

Roger,

Having written internal library code for both javac and jtreg to do what 
you suggest, I would support such an API.

I note that as well as parsing system properties, it would also be a 
useful API for command-line tools that accept paths as options.

However, I would suggest that it is more appropriate to return a 
List<Path> than a List<String>.  It is better to bias the API towards an 
appropriate type (i.e. Path) than to leave it to the user to create a 
stream to do the conversion.   Those folk that still want a File can 
still create the stream to do the conversion if they so desire.

By converting to Paths as part of the API, it becomes a clearer point to 
specify and document the possibility of InvalidPathException.

-- Jon


On 7/19/18 12:39 PM, Roger Riggs wrote:
> Hi,
>
> Parsing of paths such as the values of properties java.class.path and 
> java.library.path
> do not have  direct support in the Java API.
> There are several implementations within OpenJDK and a few variations 
> exist with regard to
> treatment of empty path elements and on Windows support for quoting.
>
> Would it be useful to have an API such as the following:
>
>     /**
>      * Returns a list of paths parsed from a string separated by 
> {@link File#pathSeparator}.
>      * All characters except the {@link File#pathSeparator} are allowed.
>      * Some operating systems support quoting segments of the string
>      * potentially including {@code pathSeparator} characters.
>      * Empty paths, identified by leading, trailing, and adjacent 
> separator characters,
>      * can be omitted or replaced with a non-null provided path.
>      *
>      * @implNote
>      * On Windows, zero or more characters between double-quotes 
> ({@code "}) are included
>      * literally in the path, regardless of whether they are valid in 
> a path.
>      *
>      * @param path a string containing paths separated by the {@link 
> File#pathSeparator}
>      * @param emptyPath a path to replace an empty path or {@code 
> null} to ignore empty paths
>      * @return an immutable list of strings for each path; {@code 
> non-null}
>      */
>     public static List<String> parsePathStrings(String path, String 
> emptyPath) { ...}
>
> There are of course, possible variations and convenience versions but 
> the API should be kept to the essentials.
> With java.util.streams it becomes easy to process each component or to 
> map the strings to Files or Path.
>
> Suggestions welcome, Roger
>