NullPointerException error with objects in array

Question

I'm new to java ,and I get this error on compiler

Enter name : pot Exception in thread "main" java.lang.NullPointerException at account.BankTest.main(BankTest.java:17) C:\Users\Carl the INVOKER\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1 BUILD FAILED (total time: 7 seconds)

Class Account

package account;

public class Account {
    private String name;
    private String surname;
    private int age;
    private int sex;

    public Account(String name, String surname, int age, int sex) {
        this.name = name;
        this.surname = surname;
        this.age = age;
        this.sex = sex;
    }

    public Account() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;

    }

    public String getSurname() {
        return surname;
    }

    public void setSurname(String surname) {
        this.surname = surname;

    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getSex() {
        return sex;
    }

    public void setSex(int sex) {
        this.sex = sex;
    }
}

Class BankTest

package account;

import java.util.Scanner;

public class BankTest {

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

        Account user[] = new Account[10];

        System.out.println("Enter name : ");
        user[1].setName(scan.nextLine());

        System.out.println(user[1].getName());
    }
}

Has this thread been resolved? It would help a lot for other users and myself if you marked a solved problems. If you have found a better solution, please share with the community. — EyuelDK
– EyuelDK, Commented Apr 26, 2017 at 4:18
I didn't use object arrays , i use ArrayLists. The code which is your suggested didn't work. — Suat Alkan
– Suat Alkan, Commented Apr 26, 2017 at 20:27
This is an object array Account user[] = new Account[10]; not an ArrayList. An ArrayList would be something like this List<Account> user = new ArrayList<Account>(); — EyuelDK
– EyuelDK, Commented Apr 26, 2017 at 20:30
Either way, just do this as proof that you did not initialize the elements of your array. Put System.out.println(user); in your code before your scanner reads nextLine you'll see that you have an array of null. — EyuelDK
– EyuelDK, Commented Apr 26, 2017 at 20:32

EyuelDK · Accepted Answer · 2017-04-23 20:40:20Z

0

Your array has no values in it. Account user[] = new Account[10]; only creates the array, but doesn't initialize the elements in the array. Therefore, when you execute this statement user[1].setName(scan.nextLine());, user[1] doesn't reference an Account object, it actually references a null value; thus, calling the method setName will throw a NullPointerException. To initialize your account array, you need to do something like this before accessing it.

for (int i=0: i<user.length; i++) {
    user[i] = new Account(null, null, 0, 0);
}

answered Apr 23, 2017 at 20:40

EyuelDK

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