Use `Character.getNumericValue(ch)` for numeric characters and many Unicode digits
Use `ch – ‘0’` for digit characters `’0’` to `’9’`
Use `Integer.parseInt(String.valueOf(ch))` for a single digit character
Use `Character.digit(ch, 10)` to convert a digit character in base 10
Use `(int) ch` to get the character’s Unicode code point value
Use `((int) ch) – 48` for ASCII digit characters `’0’` to `’9’`