question: private String extractBoundary ( String line ) { int index = line . lastIndexOf ( "boundary=" ) ; if ( index == - 1 ) { return null ; } String boundary = line . substring ( index + 9 ) ; if ( boundary . charAt ( 0 ) == '"' ) { index = boundary . lastIndexOf ( '"' ) ; boundary = boundary . substring ( 1 , index ) ; } boundary = "--" + boundary ; return boundary ; }
target:  Extracts and returns the boundary token from a line.