Use direct cast: `(int) ch`
Use `Character.getNumericValue(ch)` for digit characters and some letters
Use `Character.digit(ch, 10)` for base-10 digit characters
Use arithmetic with `’0’`: `ch – ‘0’` for numeric digits
Use `Integer.valueOf(String.valueOf(ch))` for a single digit character as a string
Use `String.valueOf(ch).charAt(0)` only if converting through string is needed