Hey, Byron.
There is a whole set of new path-related classes and methods proposed
for Java 7. I'd suggest you file a bug against Java 6 for this. I
doubt anything will happen to the File class and the methods you've
described, but it might help make sure that the new path-related APIs do
the right thing.
- Tim
Lloyd L Chambers wrote:
> Thanks Byron, a good tip.
>
> On May 17, 2008, at 11:04 AM, Byron Nevins wrote:
>
>> Say you are given a java.io.File object that was made like so:
>>
>> File f = new File("/foo/./././goo");
>>
>> Say that you need a File object for the parent dir -- which is "/foo"
>> in this case.
>>
>> If you do this:
>>
>> File parent = f.getAbsoluteFile().getParentFile()
>>
>> parent will be "/foo/././"
>> File grandparent = parent.getParentFile()
>>
>> grandparent will be "/foo/."
>>
>> I.e. getParent and getParentFile are pretty dumb. They just strip
>> off the last path seperator without looking at it.
>>
>> Now if you do the following with the original file, you get the
>> "real" parent dir. This is the trick.
>>
>> *File parent = new File(f, "..");
>> parent --> "/foo"
>> *
>> ------------------------------
>> I.e. never call getParent or getParentFile -- it will not work with
>> relative path portions.
>> instead use the File constructor with ".." as the filename.
>> -------------------------------
>>
>> Another possible solution is to sanitize the original File with
>> getCanonicalFile() to get rid of the relative path portions.
>> this has 3 problems -
>>
>> 1) Your path will have error-prone and unneccessary (usually)
>> backslashes in Windows
>> 2) It's more work and requires a try/catch block
>> 3) It handles symbolic link files differently
>>
>> The reason I'm sending this tip out is that I got burned by this
>> behavior. I had code that was getting a crucial parent directory.
>> It was working fine for months. Then in code a hundred levels above
>> it, a "." was inserted just before the final directory name. KABOOM.
>>
>> Ref: http://bt2ws.central.sun.com/CrPrint?id=6687287
>> --
>> Byron Nevins Work 408-276-4089, Home 650-359-1290, Cell 650-784-4123 - Sun Microsystems, Inc.
>
> ---
> Lloyd L Chambers
> lloyd.chambers_at_sun.com <mailto:lloyd.chambers_at_sun.com>
> Sun Microsystems, Inc
>
>
>