Creating a path between two paths in Java using the Path class

Question

What does exactly mean this sentence from this oracle java tutorial:

A relative path cannot be constructed if only one of the paths includes a root

Answer 1

As other answers already mentioned this is due to the different roots in the path.

To work around that, you can use toAbsolutePath().

For example:

public class AnotherOnePathTheDust {
  public static void main (String []args)
  {
    Path p1 = Paths.get("home").toAbsolutePath();
    Path p3 = Paths.get("/home/sally/bar").toAbsolutePath();

    Path p1_to_p3 = p1.relativize(p3);

    Path p3_to_p1 = p3.relativize(p1);
    System.out.println(p3_to_p1);
  }
}