// code uses a nested if (Serial.available() > 0 ) { ... }

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Enter a string and press Enter:");
}

void loop() {
  if (Serial.available() > 0) {
    char ch = Serial.read();
    String str = "";               // create an Arduino String object
    
    while (ch != '\n') {
      if (ch >= 32 && ch <= 126) { // check if the character is printable
        str += ch;                 // append the character to the string
      }
      if (Serial.available() > 0) {
        ch = Serial.read();        // read the next character
      }
    }

    Serial.print("Received String: ");
    Serial.println(str);
    Serial.println("Enter another string and press Enter:");
  }
}