16x2 LCD and 4X4 Keypad unlock for Arduino

passLock.ino

#include <Wire.h>
#include <LiquidCrystal.h>
#include <SoftwareSerial.h>
#include <Keypad.h>

#define redLED 13
#define greenLED 10
#define relayPIN 12

String password = "2468";
String enteredString;

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[ROWS] = {5, 4, 3, 2}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {9, 8, 7, 6}; //connect to the column pinouts of the keypad

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );
LiquidCrystal lcd (A0, A1, A2, A3, A4, A5);

void setup(){
  isLocked(false);
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("     Welcome");
  lcd.setCursor(0, 1);
  lcd.print(" Enter Password");
  pinMode(redLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
  
  Serial.begin(9600);
  Serial.print("Hello World");
}
  
void loop(){
  char key = keypad.getKey();
  if (key){
    enteredString = enteredString + key;
    clearScreen();
    lcd.print(" Enter Password ");
    lcd.setCursor(0, 1);
    lcd.print("      " + enteredString + "      ");
    if(enteredString.length() == 4){
      if(enteredString == password){
        enteredString = "";
        clearScreen();
        lcd.print("    Unlocked    ");
        isLocked(true);
      } else if (enteredString.length() > 4) {
        clearScreen();
        lcd.print("    Incorrect   ");
        isLocked(false);
        enteredString = "";
      } else {
      clearScreen();
        lcd.print("    Incorrect   ");
        isLocked(false);
        enteredString = "";
      }
    }
  }
}

void isLocked(int locked){
  if(locked){
    digitalWrite(relayPIN, LOW);
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH);
  }
  else{
    digitalWrite(relayPIN, HIGH);
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);
  }
}

void clearScreen(){
  for (int i = 0; i < 16; ++i){
    lcd.setCursor (i, 1);
    lcd.write(' ');
    lcd.setCursor (i, 2);
    lcd.write(' ');
  }
  lcd.setCursor(0, 0);
}