Generating an alphabetic sequence in Java

Question

I'm looking for a way of generating an alphabetic sequence:

A, B, C, ..., Z, AA, AB, AC, ..., ZZ. 

Can anyone suggest a convenient way of doing this. What data structures can I make use of?

I'd like methods which get the next code in the sequence and then reset the sequence.

Answer 1

A one-line recursive function to generate the string from an integer:

static String str(int i) {     return i < 0 ? "" : str((i / 26) - 1) + (char)(65 + i % 26); } 

Example usage:

public static void main(String[] args) {     for (int i = 0; i < 27*27; ++i) {         System.out.println(i + " -> " + str(i));     } } 

Output:

0 -> A 1 -> B 2 -> C [...] 24 -> Y 25 -> Z 26 -> AA 27 -> AB [...] 700 -> ZY 701 -> ZZ 702 -> AAA 703 -> AAB [...] 727 -> AAZ 728 -> ABA 

Answer 2

I combined Wikipedia's Hexavigesimal#Bijective base-26 and Bijective numeration#Properties of bijective base-k numerals to make this:

import static java.lang.Math.*;  private static String getString(int n) {     char[] buf = new char[(int) floor(log(25 * (n + 1)) / log(26))];     for (int i = buf.length - 1; i >= 0; i--) {         n--;         buf[i] = (char) ('A' + n % 26);         n /= 26;     }     return new String(buf); } 

With the help of Wolfram Alpha. Maybe it would have been simpler to just use the implementation in the first link though.