Java中的方法实现

Question

How do I add input to the HashSet in the given problem. I mainly want to use the addEmployee, removeEmployee, printEmployee methods in the Manager class, but I can't figure out what to write in the main method so that the addEmployee, removeEmployee and printEmployee methods of Manager class are invoked

public class EmployeeTest
{
   public static void main(String[] args) 
   {
      Manager mgr = new Manager(207, "Barbara Johnson", "054-12-2367", 109_501.36, "US Marketing");
      Employee e=new Employee(127, "Kyle Jenner", "023-42-5368", 123_243.90); // newly edited
      mgr.addEmployee(e); //newly edited
      mgr.printEmployee(e); //newly edited
      printEmployee(mgr);
   }
   public static void printEmployee(Employee emp) 
   {
      System.out.println(); 
      System.out.println("Employee id:         " + emp.getEmpId());
      System.out.println("Employee name:       " + emp.getName());
      System.out.println("Employee Soc Sec #:  " + emp.getSsn());
      System.out.println("Employee salary:     " + NumberFormat.getCurrencyInstance().format((double) emp.getSalary()));          
   }
}

public class Employee 
{
  private int Id;
  private String name;
  private String ssn;
  private double salary;
  public Employee(int Id, String name, String ssn, double salary)
  {
     this.Id = Id;
     this.name = name;
     this.ssn = ssn;
     this.salary = salary;
  }
  public int getEmpId() 
  {
     return Id;
  }
  public String getName() 
  {
     return name;
  }
  public String getSsn()
  {
     return ssn;
  }
  public double getSalary() 
  {
     return salary;
  }
  public void setName(String name) 
  {
     if (name != null && !name.equals("")) 
     {
         this.name = name;
     }
  }
  public void raiseSalary(double increase) 
  {
     if (increase > 0) 
     {
         salary += increase;

     }
  }
}

public class Manager extends Employee 
{
  private String dept;
  public Manager(int Id, String name, String ssn, double salary, String dept)
  {
     super(Id, name, ssn, salary);
     this.dept = dept;
  }
  **private Set<Employee> staff=new HashSet<>();**  //This is where I need help
  **public void addEmployee(Employee e)**  //This is where I need help
  {
     staff.add(e);
  }
  **public void removeEmployee(Employee e)**  //This is where I need help
  {
     staff.remove(e);
  }
  **public void printEmployee(Employee e)**  //This is where I need help
  {
     for (Employee emp: staff)
     {
        System.out.println("Name : "+getName()+" "+"ID : "+getEmpId());
     }
  }
  public String getDeptName()
  {
     return dept;
  }
}

Output Of Program

Name : Barbara Johnson ID : 207 //Desired Output:- Name : Kyle Jenner ID : 127

Employee id: 207

Employee name: Barbara Johnson

Employee Soc Sec #: 054-12-2367

Employee salary: Rs.109,501.36

Testing raiseSalary and setName on Manager:

Employee id: 207

Employee name: Barbara Johnson-Smythe

Employee Soc Sec #: 054-12-2367

Employee salary: Rs.119,501.36

Answer 1

Since the static type of emp in printEmployee() is Employee you can use only the method which are defined in Employee (or defined there and overriden in Manager ). Since printEmployee() is defined in Manager it can be used only in variables declaed as Manager

Answer 2

Your output shows the managers name because Manager.printEmployee() is calling get getName() and getEmpID() on the Manager object, not on its employees.

**public void printEmployee(Employee e)**  //This is where I need help
{
  for (Employee emp: staff)
  {
     System.out.println("Name : "+getName()+" "+"ID : "+getEmpId()); 
  } 
}

(In addition, this method receives a reference e to an Employee object that it then ignores.)

Remember how you modified printEmployee(e); to mgr.printEmployee(e); to call the method on the Manager object referenced by mgr? You'll need to do the same thing to call the method's on the Employee objects.

public class Manager extends Employee {
   **public void printEmployee()**  //This is where I need help
   {
      for (Employee emp: staff)
      {
         System.out.println("Name : "+emp.getName()+" "+"ID : "+emp.getEmpId()); 
      } 
   }
   ...

Here's the key thing to remember. You're not just calling a set of functions. You're interacting with objects by calling methods on them. If you want to interact with an object, you have to call methods through a reference to that object -- as you've done with mgr.addEmployee() in the main() method.