FindBugs complains if you ignore the error return value from a filesystem
operation, e.g.,
f.mkdirs();
Be careful when fixing these errors. In many cases it's ok if the operation
fails, e.g., if the directory already exists. The fix for the above is NOT
if (!f.mkdirs())
error(); // WRONG
A better fix is
if (!f.isDirectory() && !f.mkdirs())
error();
Also, be careful with filesystem operations that might behave differently
on Windows. I recently got bit by some permission changing code. When I
fixed it to fail if the permissions weren't changed, it failed on Windows.
The permission changing method as currently implemented always fails on
Windows. Ouch. In this case I chose to always ignore the return value.