question: private static String doGetFullPath ( String filename , boolean includeSeparator ) { if ( filename == null ) { return null ; } int prefix = getPrefixLength ( filename ) ; if ( prefix < 0 ) { return null ; } if ( prefix >= filename . length ( ) ) { if ( includeSeparator ) { return getPrefix ( filename ) ; } else { return filename ; } } int index = indexOfLastSeparator ( filename ) ; if ( index < 0 ) { return filename . substring ( 0 , prefix ) ; } int end = index + ( includeSeparator ? 1 : 0 ) ; if ( end == 0 ) { end ++ ; } return filename . substring ( 0 , end ) ; }
target:  Does the work of getting the path.