Incompatible types: Object cannot be converted to another Object?

Question

I am trying to work out what may be causing this problem for a while now. I am completely new to Java and BlueJ but have been looking at this for hours and cannot figure out what is causing the problem. Keep getting the error message "Incompatible types: Plasterer cannot be converted to Apprentice". Any help is greatly appreciated.

//Purpose of Program: To create a mixed array to hold 2 different Apprentice objects - Plasterer and Carpenter //Plasterer and Carpenter //All the details of each object are then displayed to the screen.

public class MixedLists
{

  public static void main(String args[])
  {

    //Declaration of object list to hold 2 student objects
    Apprentice [] apprenticeList = new Apprentice[2];

    ////////////////////////////////////////////////////////////////////
    //Plasterer
    //Taking in values
    String NameIn, NumberIn, AddressIn, StudentIDIn, EmployerNameIn, FinalSem1GradeIn;

    System.out.println("Entering data for Plasterer");
    //Apprentice class attributes
    System.out.print("\tEnter Name:                   ");
    NameIn = EasyScanner.nextString();

    System.out.print("\tEnter telephone number:       ");
    NumberIn = EasyScanner.nextString();

    System.out.print("\tEnter Address:                ");
    AddressIn = EasyScanner.nextString();

    System.out.print("\tEnter student id:             ");
    StudentIDIn = EasyScanner.nextString();      

    //Plasterer class attributes
    System.out.print("\tEnter in Employer Name:         ");
    EmployerNameIn = EasyScanner.nextString();

    System.out.print("\tEnter Final Semester 1 Grade:    ");
    FinalSem1GradeIn = EasyScanner.nextString();

    //Initializing what is referenced by position 0 of the object list with a plasterer object
    apprenticeList[0]=new Plasterer(NameIn, NumberIn, AddressIn, StudentIDIn, EmployerNameIn, FinalSem1GradeIn);

    System.out.println("\n");

    /////////////////////////////////////////////////////////////////   
    //Carpenter
    String NameIn1,AddressIn1,Number1,StudentID1;
    //additional variables
    String awardSought,specialisation;
    double gpaModuleGrade, industrialExperienceMark;

    //Entering values for Carpenter
    System.out.println("Entering data for Carpenter");
    //Apprentice class attributes
    System.out.print("\tEnter Name:                   ");
    NameIn1 = EasyScanner.nextString();

    System.out.print("\tEnter telephone number:       ");
    Number1 = EasyScanner.nextString();

    System.out.print("\tEnter Address:                ");
    AddressIn1= EasyScanner.nextString();

    System.out.print("\tEnter student id:             ");
    StudentID1= EasyScanner.nextString();

    //Carpenter class attributes    
    System.out.print("\tEnter award sought:           ");
    awardSought = EasyScanner.nextString();
    System.out.print("\tEnter specialist area:        ");
    specialisation = EasyScanner.nextString();

    //Carpenter class attributes
    System.out.print("\tEnter GPA Module Grade:       ");
    gpaModuleGrade = EasyScanner.nextString();
    System.out.print("\tEnter industrial experience Grade: ");
    industrialExperienceMark = EasyScanner.nextString();

    //Initializing what is referenced by position 1 of the object list with a Carpenter object
    apprenticeList[1]=new Carpenter(NameIn1, AddressIn1, Number1, StudentID1,awardSought,specialisation, gpaModuleGrade,industrialExperienceMark);

    System.out.println("\n");

    ////////////////////////////////////////////////////////////////////
    //for loop to display out contents of mixed object array
    //Display out all information associated with Carpenter, Carpenter and CabinetMaker

    System.out.println("Award Details for all Apprentices in the System\n"); 
    for(int i = 0; i < apprenticeList.length; i++)
    {
        System.out.println(apprenticeList[i].printAwardDetails());
    }

  }
}

The Apprentice Class goes as such

public abstract class Apprentice
{
    //attributes

    private String Name;
    private String Number;
    private String Address;
    private String StudentID;

    public Apprentice (String NameIn, String NumberIn, String AddressIn, String StudentIDIn)
    {
        Name = NameIn;
        Number = NumberIn;
        Address = AddressIn;
        StudentID  = StudentIDIn;
    }

        //Methods to read the attributes

        public String getName()
        {
            return Name;
        }

        public String getNumber()
        {
            return Number;
        }

    public String getAddress()
    {
        return Address;
    }

    public String getStudentID ()
    {
        return StudentID ;
    }

    public void setName(String NameIn)
    {
        Name = NameIn;
    }

    public void setNumber(String NumberIn)
    {
        Number = NumberIn;
    }

    public void setAddress(String AddressIn)
    {
        Address = AddressIn;
    }

    public void setStudentID (String StudentIDIn )
    {
        StudentID  = StudentIDIn;
    }

}

Answer 1

You need to use inheritance.

Create a class named for example "Worker", then Plasterer and Apprentice should both inherit that class. You then can have a list of workers containing both Plasterers and Apprentice.

Or if "Apprentice" is just a type of Plasterer, make Apprentice inherit Plasterer (or the opposite if Plasterer is a kind of Apprentice)