java缓冲阅读器，如何使用br.readLine(System.in)读取一行并将其转换为char?

I have to do a cryptography program in Java which takes a number and a string(as an instance variable) from the user and adds that number to the ASCII of each letter in the string to create a new String.For example, if the number is 2 and the original string is "ABCXYZ" it should print "CDEZAB" This is what I've got so far:I have to do a cryptography program in Java whi