The type java.io.Serializable cannot be resolved. It is indirectly referenced from required .class files

I'm writing a code where I need HashMap, but it throws an error:

The type java.io.Serializable cannot be resolved. It is indirectly referenced from required .class files

I tried to import java.io.Serializable but it says cannot be resolved. I tried to find solutions but they are all related to updating pom files etc, in my case I'm just creating a simple java class.

JDK Version: jdk-11.0.9

Here is my code:

import java.util.HashMap;
import java.util.Scanner;

public class BankApp {

  static String getMainMenu() {
    String menuChoice;
    Scanner in = new Scanner(System.in);

    System.out.println("-----------*************-----------");
    System.out.println("Choose an option:");
    System.out.println("1. Add New Customer");
    System.out.println("2. Search Existing Customer");
    System.out.println("-----------*************-----------");
    System.out.print("Enter your choice: ");
    menuChoice = in.nextLine();
    in.close();
    return menuChoice;
  }

  static Customer register() {
    String id;
    String name;
    String gender;
    String location;
    int accountType;
    int accountNo;
    Scanner in = new Scanner(System.in);

    System.out.println("-----------*************-----------");
    System.out.print("Enter ID No.: \t");
    id = in.nextLine();
    System.out.print("Enter Name: \t");
    name = in.nextLine();
    System.out.print("Enter Gender(M/F): \t");
    gender = in.nextLine();
    System.out.print("Enter Location: \t");
    location = in.nextLine();
    System.out.print("Enter A/C Type(0 = Savings, 1 = Current): \t");
    accountType = in.nextInt();
    System.out.print("Enter A/C No: \t");
    accountNo = in.nextInt();
    System.out.println("-----------*************-----------");
    in.close();

    return new Customer(id, name, gender, location, accountType, accountNo);
  }
  
  public static void main(String ...args) {
    HashMap<String, Customer> customerMap = new HashMap<String, Customer>(); 
    String mainMenuChoice = BankApp.getMainMenu();

    switch(mainMenuChoice) {
      case "1":
        Customer newCustomer = BankApp.register();
        System.out.println(newCustomer.name);
        customerMap.put(newCustomer.id, newCustomer);
        break;
      default:
        break;  
    }
  }
}

class Customer {

  String id;
  String name;
  String gender;
  String location;
  int accountType;
  int accountNo;

  Customer(String id, String name, String gender, String location, int accountType, int accountNo) {
    this.id = id;
    this.name = name;
    this.gender = gender;
    this.location = location;
    this.accountType = accountType;
    this.accountNo = accountNo;
  }

  public void print() {
    System.out.println("-----------*************-----------");
    System.out.print("ID: \t" + this.id);
    System.out.print("Name: \t" + this.name);
    System.out.println("Gender: \t" + this.gender);
    System.out.println("Location: \t" + this.location);
    System.out.format("A/C Type: \t%d", this.accountType);
    System.out.format("A/C No.: \t%d", this.accountNo);
    System.out.println("-----------*************-----------");
  }
}