question: public static long sizeOfDirectory ( File directory ) { checkDirectory ( directory ) ; final File [ ] files = directory . listFiles ( ) ; if ( files == null ) { return 0L ; } long size = 0 ; for ( final File file : files ) { try { if ( ! isSymlink ( file ) ) { size += sizeOf ( file ) ; if ( size < 0 ) { break ; } } } catch ( IOException ioe ) { } } return size ; }
target:  Counts the size of a directory recursively (sum of the length of all files).