The formatIndex method returns the supplied integer as a string formatted using the specified numerical system. The integer can be formatted using one of the following formats:

• 1
  standard numbering system
• 01
  standard numbering with leading zeros
• A
  uppercase sequence: A-Z, AA-ZZ
• a
  lowercase sequence: a-z, aa-zz
• I
  uppercase Roman numerals: I, II, III, IV, ...
• i
  lowercase Roman numerals: i, ii, iii, iv, ...