question: private static String normalize ( StringBuilder sb , String path , int off ) { int len = path . length ( ) ; off = nextNonSlash ( path , off , len ) ; int start = off ; char lastC = 0 ; while ( off < len ) { char c = path . charAt ( off ) ; if ( isSlash ( c ) ) { if ( lastC == ' ' ) throw new InvalidPathException ( path , "Trailing char <" + lastC + ">" , off - 1 ) ; sb . append ( path , start , off ) ; off = nextNonSlash ( path , off , len ) ; if ( off != len ) sb . append ( '\\' ) ; start = off ; } else { if ( isInvalidPathChar ( c ) ) throw new InvalidPathException ( path , "Illegal char <" + c + ">" , off ) ; lastC = c ; off ++ ; } } if ( start != off ) { if ( lastC == ' ' ) throw new InvalidPathException ( path , "Trailing char <" + lastC + ">" , off - 1 ) ; sb . append ( path , start , off ) ; } return sb . toString ( ) ; }
target:  Remove redundant slashes from the rest of the path, forcing all slashes into the preferred slash.