StringBuilder sb = new StringBuilder("a");
String s = sb.toString();
sb.append("b");
System.out.println(s);

char c = 'A';
c += 2;
System.out.println(c);

int s = 0;
for (int i = 1; i <= 4; i++) {
  if (i % 2 == 1) continue;
  s += i;
}
System.out.println(s);