CODEWITHSUNDEEP
javaclassmethodsconstructorhashset
M.Throw
M.Throw

Reputation: 145

Creating a new instance of a class from another class

So I'm stuck on some homework trying to create an instance of the Employee class from my class called records.

public class Employee implements Comparable<Employee>

{
/* instance variables */
private String Name;
private String employeeNumber;


/**
 * Constructor for Employee
 */
public Employee(String employNum)
{
   super();
   this.employeeNumber = employNum;             
}

Next I need to create a Record class that will create a HashSet of Employees details, this is where I need help.

public class Records
{
   private HashSet employeeSet;

   public Records()
   {
      Set<Employee> employeeSet = new HashSet<Employee>();
   }

Then I want it to have a method for adding a new employee and then putting their records in the set.

   public  enrollEmployee(String num)
   {
      Employee newEmp = new Employee(num);
      employeeSet.add(newEmp);
   }
}

I can't get that last bit to create a new employee, it doesn't come out with an error and it compiles correctly. Just no new employee. *Adding the employeeSet.add(newEmp); caused a compiler warning and that method won't run due to a NullPointerException, probably because the employee isn't actually created.

For more info, when I create an employee the name should come out as "null" if only an employee number is entered but I still need to store that information.

Edited to update information. There is more detail for the Employee class which I have left out, I'm only supposed to be creating the Records class.

Last update, thank you for the help. After reading the replies this is what I got to work for me.

   public class Records
{
   private Set<Employee> employeeSet = new HashSet<Employee>();

   public Records()
   {

   }

   public void enrollEmployee(String num)
   {
      Employee newEmp = new Employee(num);
      employeeSet.add(newEmp);
   }
}

Upvotes: 1

Views: 16505

Answers (1)

DarkV1
DarkV1

Reputation: 1776

Heres the new solution based on what you are looking for in the comments

public class Record
  {
    private Set<Employee> employeeSet = new HashSet<Employee>();

    public Record()
    {
        newEmployee("1");
        newEmployee("2");
        newEmployee("3");
    }

    public void newEmployee(String employNumber)
    {
        Employee newEmp = new Employee(employNumber);
        employeeSet.add(newEmp);
    }
 }

The method that you created was never called on... So an employee was never created. Therefore, by calling on the newEmployee method in the Record Constructor, a new employee is created

Upvotes: 4

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