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POI get a nullPointerException when I'm trying to add some values to a referenced class from another class
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  1. POI get a nullPointerException when I'm trying to add some values to a referenced class from another class
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    copied!<p>I am c# programmer and I am used to c#'s syntaxes for encapsulation and other stuff.But now,due to some reasons,I should write something with java and I am practicing java for a day now!I am going to create a dummy project for my self in order to make myself more comfortable with java's oop concepts</p> <p>What I am trying to do is that I want a class named 'Employee' which has three properties(fields):<code>firstName</code>,<code>lastName</code>,and <code>id</code>.And then I want to create another class named <code>EmployeeArray</code> which will construct an array of <code>Employee</code>s within itself and can perform some operations on it(for some reasons I want this project this way!!) Now I want to add some values to the <code>Employee</code>s within the <code>EmployeeArray</code> class.here's my work so far:</p> <pre><code>//this is the class for Employee public class Employee { private String firstName; private String lastName; private int id; public void SetValues(String firstName, String lastName, int id) { this.firstName = firstName; this.lastName = lastName; this.id = id; } //this is the EmployeeArray class public class EmployeeArray { private int numOfItems; private Employee[] employee; public EmployeeArray(int maxNumOfEmployees) { employee = new Employee[maxNumOfEmployees]; numOfItems = 0; } public void InsertNewEmployee(String firstName, String lastName, int id){ try { employee[numOfItems].SetValues(firstName, lastName, id); numOfItems++; } catch (Exception e) { System.out.println(e.toString()); } } //and this is the app's main method Scanner input = new Scanner(System.in); EmployeeArray employeeArray; employeeArray = new EmployeeArray(input.nextInt()); String firstName; String lastName; int id; firstName = input.nextLine(); lastName = input.nextLine(); id = input.nextInt(); employeeArray.InsertNewEmployee(firstName, lastName, id); </code></pre> <p>the problem is I get a nullPointerException when the app wants to set the values,and it is happening in the <code>employeeArray</code> reference.I don't know what I am missing.Any suggestions?</p>
 

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