constructor of the class will be all the data except the employee number, which will be a generated number (the first employee to be employee number 1, the second employee number 2 and so on). and so on)

public class Employee {
    private int employeeNumber;
    private String employeeName;
    private String employeeAddress;
    private int employeeAge;
    private double employeeSalary;
    // private static int numberOfEmployees = 1;
    public Employee() {
        this.employeeNumber = numberOfEmployees++;
        this.employeeName = "";
        this.employeeAddress = "";
        this.employeeAge = 0;
        this.employeeSalary = 0.0;
    }
    public Employee(String employeeName, String employeeAddress, int employeeAge, double employeeSalary) {
        this.employeeNumber = numberOfEmployees++;
        this.employeeName = employeeName;
        this.employeeAddress = employeeAddress;
        this.employeeAge = employeeAge;
        this.employeeSalary = employeeSalary;
    }