How to store values in custom object array using Scanner in Java?

Question

I was given an exam, where I had to create a class and after that, I had to write two functions in which the input parameter is an object Array and took the values from user input. Below is the code that I have written. But, I repetitively got NullPointerException and InputMismatchException in line number 17 & 18. Please help me.

import java.util.Scanner;
public class Solution
{
public static void main(String[] args)
{
//code to read values
//code to call required method
//code to display the result

    Scanner sc = new Scanner(System.in);
    int tasks = sc.nextInt();
    
    Bank[] banks = new Bank[tasks];
    
    for(int i = 0; i < tasks; i++){
        int bankId = sc.nextInt();      
        String bankName = sc.next();
        int numberOfCustomers = sc.nextInt();
        // banks[i].setNumberOfCustomers(numberOfCustomers);
        String city = sc.nextLine();
        // banks[i].setCity(city);
        
        banks[i] = new Bank(bankId, bankName, numberOfCustomers, city);
    }
    
    
    String city = sc.next();
    
    if(findAvgNumberOfCustomersByCity(banks, city) != 0){
        System.out.println(findAvgNumberOfCustomersByCity(banks, city));
    }
    else{
        System.out.println("No Bank found with matching criteria.");
    }

    String ans = getBankWithMinimumNoOfCustomers(banks);
    if(ans.equals(null)){
        System.out.println("No Bank found with matching criteria.");
    }
    else{
        for(Bank b : banks){
            if(b.getBankName().equals(ans)){
                System.out.println(b.getBankId());
                System.out.println(b.getBankName());
                System.out.println(b.getNumberOfCustomers());
                System.out.println(b.getCity());
            }
        }
    }
}

//code the first method
public static double findAvgNumberOfCustomersByCity(Bank[] banks, String city){
    
    double ans = 0;
    double total = 0, totalBanks = 0;
    
    for(Bank b : banks){
        if(b.getCity().equals(city)){
            total += b.getNumberOfCustomers();
            totalBanks++;
        }
    }
    
    return (total/totalBanks);
}

//code the second method
public static String getBankWithMinimumNoOfCustomers(Bank[] banks){
    int minNumber = Integer.MAX_VALUE;
    String bankName = "";
    for(Bank b : banks){
        if(b.getNumberOfCustomers() < minNumber){
            minNumber = b.getNumberOfCustomers();
            bankName = b.getBankName();
        }
    }
    
    if(minNumber == Integer.MAX_VALUE){
        return null;
    }
    else{
        return bankName;
    }
}
}

//code the class
class Bank{
    private int bankId;
    private String bankName;
    private int numberOfCustomers;
    private String city;
    
    public Bank(int bankId, String bankName, int numberOfCustomers, String city){
        this.bankId = bankId;
        this.bankName = bankName;
        this.numberOfCustomers = numberOfCustomers;
        this.city = city;
    }
    public int getBankId(){
        return this.bankId;
    }
    public void setBankId(int bankId){
        this.bankId = bankId;
    }
    
    public String getBankName(){
        return this.bankName;
    }
    public void setBankName(String bankName){
        this.bankName = bankName;
    }
    
    public int getNumberOfCustomers(){
        return this.numberOfCustomers;
    }
    public void setNumberOfCustomers(int numberOfCustomers){
        this.numberOfCustomers = numberOfCustomers;
    }
    
    public String getCity(){
        return this.city;
    }
    public void setCity(String city){
        this.city = city;
    }
}

Anyone please help me in finding the error in my code, I was flummoxed and have tried a lot to get the answer, but unable to get so.

Vishal · Accepted Answer · 2023-07-01 09:32:30Z

The problem is in the main method when I am trying to store the values. That was not appropriate. The correct way is-

public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter the number of banks: ");
        int numBanks = scanner.nextInt();
        scanner.nextLine(); // Consume the newline character

        Bank[] banks = new Bank[numBanks];

        for (int i = 0; i < numBanks; i++) 
            int bankId = scanner.nextInt();
            scanner.nextLine(); // Consume the newline character

            String bankName = scanner.nextLine();

            int customers = scanner.nextInt();
            scanner.nextLine(); // Consume the newline character

            String bankCity = scanner.nextLine();

            banks[i] = new Bank(bankId, bankName, customers, bankCity);
        }

        String cityToFind = scanner.nextLine();
}

This is the correct way to do so.

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