Question

I experienced a strange behavior from Java

File file = new File("test.txt");
file.reName(new File("test1.txt"));

The file successfully rename from test.txt to test1.txt, but if I do

System.out.println(file.getCanonicalPath()); //This return test.txt

Is this expected? And what is a clean way to solve this?

Answer 1

Yes, this is expected. File objects are immutable, and simply represent a filename.

You can think of it like this: a File object is a reference to a file, not the file itself.

This behaviour can actually be useful – for example, imagine that you are moving a previous version of a file out of the way to avoid overwriting it (i.e. to create a backup copy). If you rename foo1.txt to foo1.bak, then the original File variable that contained foo1.txt will still contain it, and can be used to open a FileOutputStream.