equals static method
Implementation
static bool equals(String? a, String? b) {
if (a == b) return true;
if (a != null && b != null && (a.length == b.length)) {
for (int i = 0; i < a.length; i++) {
if (a.codeUnitAt(i) != b.codeUnitAt(i)) return false;
}
return true;
}
return false;
}