Question

Imagine I have a ‘base’ path object, denoting a directory, and a ‘relative’ path object denoting some file within the base.

I would expect that code to look somewhat like

AbsolutePath base = new AbsolutePath("/tmp/adirectory");
RelativePath relativeFilePath = new RelativePath("filex.txt");
AbsolutePath absoluteFile = base.append( relativeFilePath );

But in the Java API (which I don’t yet know very well) I find only File, with which I can do nothing better than

File base = new File("/tmp/adirectory");
File relativeFilePath = new File("filex.txt");
File absoluteFile = base.toString() 
                  + File.separator 
                  + relativeFilePath.toString();

Is there a better way?

Answer 1

The closest you can get with java.io.File is the File(File, String) constructor:

File base = ...;
File relative = ...;
File combined = new File(base, relative.toString());

If you can use the Path class introduced in Java 7, then you can use the resolve() method, which does exactly what you want:

Path base = ...;
Path relative = ...;
Path combined = base.resolve(relative);

Please note that if base is not an absolute path, then combined won’t be absolute either! If you need an absolute path, then for a File you’d use getAbsoluteFile() and for a Path you’d use toAbsoutePath().