String str1 = "Arduino";
String str2 = "arduino";
String str3 = "Arduino Biru";
String str4 = "Arduino";
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);

  char karakter = str1.charAt(3);
  Serial.print("karakter : ");Serial.println(karakter);
  str1.concat(str2);
  Serial.print("hasil str1.concat(str2) : ");Serial.println(str1);
  int panjangnya = str2.length();
  Serial.print("Panjang str2 : ");Serial.print(panjangnya);Serial.println(" karakter.");
  panjangnya = str3.length();
  Serial.print("Panjang str3 : ");Serial.print(panjangnya);

}

void loop() {
  // put your main code here, to run repeatedly:

}