/**

* Example from the end of Chapter 7.

*/

public class Doubloon {

public static boolean isDoubloon(String s) {

// count the number of times each letter appears

int[] counts = new int[26];

String lower = s.toLowerCase();

for (char letter : lower.toCharArray()) {

int index = letter - 'a';

counts[index]++;

}

// determine whether the given word is a doubloon

for (int count : counts) {

if (count != 0 && count != 2) {

return false;

}

}

return true;

}

public static void main(String[] args) {

System.out.println(isDoubloon("Mama")); // true

System.out.println(isDoubloon("Lama")); // false

}

}