Stealing from somebody else in another answer, this is probably the best direct implementation (if you're not going to use guava).
/**
* @param string
* @return list of characters in the string
*/
public static List characters(final String string) {
return new AbstractList() {
@Override
public Character get(int index) {
return string.charAt(index);
}
@Override
public int size() {
return string.length();
}
};
}