question: protected static String extractHeaderComponent ( String header , String component ) { String fullComponent = component + "=\"" ; int fullComponentLength = fullComponent . length ( ) ; int index1 = header . indexOf ( fullComponent ) ; if ( index1 == - 1 ) { return null ; } int index2 = header . indexOf ( "\"" , index1 + fullComponentLength ) ; if ( index2 == - 1 ) { return null ; } return header . substring ( index1 + fullComponentLength , index2 ) ; }
target:  Extract a component of a header.