The "problem" with the tabs is that they indent the text to fixed tab positions, typically multiples of 4 or 8 characters (depending on the console or editor displaying them). Your first filename is 7 chars, so the next tab stop after its end is at position 8. Your subsequent filenames however are 8 chars long, so the next tab stop is at position 12.
If you want to ensure that columns get nicely indented at the same position, you need to take into account the actual length of previous columns, and either modify the number of following tabs, or pad with the required number of spaces instead. The latter can be achieved using e.g. System.out.printf
with an appropriate format specification (e.g. "%1$13s"
specifies a minimum width of 13 characters for displaying the first argument as a string).