question: public static BinaryMessage checkAndCorrect ( BinaryMessage message , int startIndex ) { boolean parityError = message . cardinality ( ) % 2 != 0 ; int syndrome = getSyndrome ( message , startIndex ) ; if ( syndrome == 0 ) { if ( parityError ) { message . flip ( startIndex + 23 ) ; } message . setCRC ( CRC . PASSED ) ; return message ; } int original = message . getInt ( 0 , 22 ) ; int index = - 1 ; int syndromeWeight = 3 ; int errors = 0 ; while ( index < 23 ) { if ( index != - 1 ) { if ( index > 0 ) { message . flip ( index - 1 ) ; } message . flip ( index ) ; syndromeWeight = 2 ; } syndrome = getSyndrome ( message , startIndex ) ; if ( syndrome > 0 ) { for ( int i = 0 ; i < 23 ; i ++ ) { errors = Integer . bitCount ( syndrome ) ; if ( errors <= syndromeWeight ) { message . xor ( 12 , 11 , syndrome ) ; message . rotateRight ( i , startIndex , startIndex + 22 ) ; if ( index >= 0 ) { errors ++ ; } int corrected = message . getInt ( 0 , 22 ) ; if ( Integer . bitCount ( original ^ corrected ) > 3 ) { message . setCRC ( CRC . FAILED_CRC ) ; return message ; } message . setCRC ( CRC . PASSED ) ; return message ; } else { message . rotateLeft ( startIndex , startIndex + 22 ) ; syndrome = getSyndrome ( message , startIndex ) ; } } index ++ ; } } message . setCRC ( CRC . FAILED_CRC ) ; return message ; }
target:  Performs error detection and returns a corrected copy of the 24-bit message that starts at the start index.