Relativize question

[Paul Statham]

Given

	  System.out.println();
	  System.out.println("Relativize");
	  System.out.println("Path 1 C:\\Java.java");
	  System.out.println("Path 2 C:\\Java.class");
	  Path path4 = Paths.get("C:\\tmp\\Java.java");
	  Path path5 = Paths.get("C:\\tmp\\Java.class");
	  System.out.println(path4.relativize(path5));

Why does it print ..\Java.class and not .\Java.class

[Ninad Kulkarni]

Refer Java API 7 for Path link

[Paul Statham]

I have seen that yes, in fact it even has this in the API

For example, if this path is "/a/b" and the given path is "/a/x" then the resulting relative path may be "../x"

I just don't understand why it would be .. and not .

All dealings with relative paths in the past have had . to mean current directory and .. as one level up

Or is it in fact saying for example if we just take

Path p1 = Paths.get("Java.java");
Path p2 = Paths.get("Java.class");
System.out.println("Relativize: " +p1.relativize(p2));

This would give

"Relativize: ../Java.class"

Relatively it is one level up from Java.java therefore the path is "../Java.class". Does that make sense?

[Paul Statham]

Ok I have worked it out, I had to break it up into bullet points to understand it though. Here are some of my notes if it helps someone else

Path relativize(Path other)
- This method attempts to construct a relative path that when resolved against this path, yields a path that locates the same file as the given path
- Where this path and the given path do not have a root component, then a relative path can be constructed
- A relative path cannot be constructed if only one of the paths have a root component
- If this path and the given path are equal then an empty path is returned
- /a/b -> /a/b/c/d = c/d
- a/b -> a/b/c/d = c/d
- /a/b/c/d -> a/b = IllegalArgumentException
- /a/b/c/d -> /a/b = ../..
- /a/b -> /a/b = ""
- /a/b -> /a/c = ../c
- /x/d/g/a/b -> /a/b = ../../../../../a/b