question: public static int jdkToClassVersion ( @ NotNull String version ) { int dot = version . indexOf ( '.' ) ; if ( dot != - 1 ) { dot ++ ; int end = version . length ( ) ; for ( int i = dot ; i < end ; i ++ ) { if ( ! Character . isDigit ( version . charAt ( i ) ) ) { end = i ; break ; } } if ( end > dot ) { int major = Integer . valueOf ( version . substring ( dot , end ) ) ; if ( major > 0 ) { return major + 44 ; } } } return - 1 ; }
target:  Converts a JDK string like 1.6.0_65 to the corresponding class file version number, e.g. 50 