Java splitting the filename into a base and extension

Question

Is there a better way to get file basename and extension than something like  File f       String name   f getName    int dot   name lastIndexOf       String base    dot    -1    name   name substring 0  dot   String extension    dot    -1         name substring dot 1

User · Answer

File extensions are a broken concept  And there exists no reliable function for it  Consider for example this filename   archive tar gz   What is the extension  DOS users would have preferred the name archive tgz  Sometimes you see stupid Windows applications that first decompress the file  yielding a  tar file   then you have to open it again to see the archive contents   In this case  a more reasonable notion of file extension would have been  tar gz  There are also  tar bz2   tar xz   tar lz and  tar lzma file  extensions  in use  But how would you decide  whether to split at the last dot  or the second-to-last dot   Use mime-types instead   The Java 7 function Files probeContentType will likely be much more reliable to detect file types than trusting the file extension  Pretty much all the Unix Linux world as well as your Webbrowser and Smartphone already does it this way

User · Answer

You can also user java Regular Expression  String split   also uses the expression internally  Refer http   download oracle com javase 1 4 2 docs api java util regex Pattern html

User · Answer

I know others have mentioned String split  but here is a variant that only yields two tokens  the base and the extension    String   tokens   fileName split                       For example    test cool awesome txt  split                       Yields     test cool awesome    txt     The regular expression tells Java to split on any period that is followed by any number of non-periods  followed by the end of input  There is only one period that matches this definition  namely  the last period    Technically Regexically speaking  this technique is called zero-width positive lookahead     BTW  if you want to split a path and get the full filename including but not limited to the dot extension  using a path with forward slashes        String   tokens   dir split                      For example       String dir     foo bar bam boozled        String   tokens   dir split                               foo bar bam    boozled

User · Answer

Source  http   www java2s com Code Java File-Input-Output Getextensionpathandfilename htm  such an utility class    class Filename     private String fullPath    private char pathSeparator  extensionSeparator     public Filename String str  char sep  char ext        fullPath   str      pathSeparator   sep      extensionSeparator   ext         public String extension         int dot   fullPath lastIndexOf extensionSeparator       return fullPath substring dot   1          public String filename        gets filename without extension     int dot   fullPath lastIndexOf extensionSeparator       int sep   fullPath lastIndexOf pathSeparator       return fullPath substring sep   1  dot          public String path         int sep   fullPath lastIndexOf pathSeparator       return fullPath substring 0  sep           usage   public class FilenameDemo     public static void main String   args        final String FPATH     home mem index html       Filename myHomePage   new Filename FPATH                 System out println  Extension       myHomePage extension         System out println  Filename       myHomePage filename         System out println  Path       myHomePage path

User · Answer

What s wrong with your code  Wrapped in a neat utility method it s fine   What s more important is what to use as separator  mdash  the first or last dot  The first is bad for file names like  setup-2 5 1 exe   the last is bad for file names with multiple extensions like  mybundle tar gz

User · Answer

http   docs oracle com javase 6 docs api java io File html getName    From http   www xinotes org notes note 774     Java has built-in functions to get the basename and dirname for a given file path  but the function names are not so self-apparent    import java io File   public class JavaFileDirNameBaseName       public static void main String   args        File theFile   new File     foo bar baz txt        System out println  Dirname      theFile getParent         System out println  Basename      theFile getName

User · Answer

Maybe you could use String split  To answer your comment   I m not sure if there can be more than one   in a filename  but whatever  even if there are more dots you can use the split  Consider e g  that   String input    boo and foo    String   result   input split         This will return an array containing      boo    and    foo      So you will know that the last index in the array is the extension and all others are the base

User · Answer

Old question but I usually use this solution   import org apache commons io FilenameUtils   String fileName     abc defg file txt    String basename   FilenameUtils getBaseName fileName   String extension   FilenameUtils getExtension fileName   System out println basename      file System out println extension      txt  NOT   txt

[java] Java: splitting the filename into a base and extension

File extensions are a broken concept

Use mime-types instead.

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