ما سبب ظهور الخطأ java.lang.nullpointerexception فى الكود؟

package com.company;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {


        Scanner in = new Scanner(System.in);


        char con = 'y';
        int su = 0;
        Account[] accounts = new Account[10];
        System.out.println(accounts.length);
       // while (con == 'y') {


            System.out.println(" أهلا وسهلا بك ");
            System.out.println(" قم ادخال بيانات الفاتورة ");
            System.out.println("ادخل اسم الزبون   ");

            String cn = in.next();
            accounts[su].setUserName(cn);
           System.out.println(accounts[su].getUserName());

            System.out.println("ادخل رقم الزبون ");
            int cno = in.nextInt();
            accounts[su].setUserID(cno);

            System.out.println("ادخل عدد العناصر  ");
            int count = in.nextInt();
            accounts[su].setCount(count);

            System.out.println("ادخل قيمة الفاتورة   ");
            int sal = in.nextInt();
            accounts[su].setSalary(sal);

            System.out.println("ادخل قيمة الخصم    ");

            accounts[su].setDiscount(in.nextDouble());
            int a = 1;
            for (int i = 0; i < a; i++) {
                System.out.println("ادخل جنس الزبون  ");
                try {
                    a++;
                    accounts[su].setGender(Gender.valueOf(in.next()));

                } catch (Exception e) {
                    i = -1;
                    System.out.println("يرجى ادخال الجنس بصيغة صحيحة xx or xy ");
                }
            }


            System.out.println(" ماذا تريد ان تفعل ");
            System.out.println(" *********** " +
                    "طباعة كل البيانات(1) " +
                    "طباعة الاسم ورقم الفاتورة)2( " +
                    "طباعة سعر الفاتورة(3)" +
                    "طباعة جميع  الفواتير (4)" +
                    "اضافة فاتورة اخرى(5))" +
                    "الخروج من البرنامج(6)) ");

            int w2 = in.nextInt();

            switch (w2) {
                case 1:
                    System.out.println("أدخل رقم الفاتورة المراد طباعتها " +
                            "(عددالفواتير الموجودة =" + accounts.length);
                    int f = in.nextInt();
                    System.out.println(accounts[f].toString());
                    break;

                case (2):
                    System.out.println("أدخل رقم الفاتورة المراد طباعتها " +
                            "(عددالفواتير الموجودة =" + accounts.length);
                    int s = in.nextInt();
                    System.out.println(accounts[s].nameiduser());
                    break;
                case 3:

                    System.out.println(accounts[su].getSalary());
                    break;
                case 4:
                    for (Account account : accounts) {
                        System.out.println(account.getSalary());
                    }
                    break;
                case 5:

                    System.out.println("wait ...");
                    su++;
                    break;

                case 6:
                    System.exit(0);

            }
        }

    }

package com.company;

public enum Gender {
    xy,xx

}

package com.company;

public class Account {
    private int userID;
    private String userName;
    private double discount;
    private int count;
    private int salary;
    private Gender gender ;

    public Gender getGender() {
        return gender;
    }

    public void setGender(Gender gender) {
        this.gender = gender;
    }

    public int getSalary() {
        return salary;
    }

    public int setSalary(int salary) {
        int newSalary = 0;
        if (salary == 101) {
            newSalary = 100;
        } else {
            newSalary=salary;
        }
        return newSalary;
    }


    public Account(int userID, String userName, double discount, int count, int salary, Gender gender) {
        this.userID = userID;
        this.userName = userName;
        this.discount = discount;
        this.count = count;
        this.salary = salary;
        this.gender = gender;
    }

    public Account(int userID, String userName, double discount, int count, int salary) {
        this.userID = userID;
        this.userName = userName;
        this.discount = discount;
        this.count = count;
        this.salary = salary;
    }

    public Account(){};


    public int getUserID() {
        return userID;
    }

    public void setUserID(int userID) {
        this.userID = userID;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public double getDiscount() {
        return discount;
    }

    public void setDiscount(double discount) {
        this.discount = discount;
    }

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    @Override
    public String toString() {
        return "Account{" +
                "userID=" + userID +
                ", userName='" + userName + '\'' +
                ", discount=" + discount +
                ", count=" + count +
                ", salary=" + salary +
                '}';
    }
    public String nameiduser() {
        return "Account{" +
                "userID=" + userID +
                ", userName='" + userName + '\'' +

                '}';
    }
}

 

كلمات دليلية: erorr java runtimeeroor