当 ArrayList 和构造函数/getter 存储另外两个类时，如何从一个类添加到 ArrayList

Question

I have 3 classes, Session , Employee , and Employees . The Employee class has the constructors and getters, the Employees class has the ArrayList , and I'm trying to add to that ArrayList within the Session class.

public class Employee {
    public Employee(String name, String email){
        this.name = name;
        this.email = email;
    }

    public String getName(){
        return name;
    }

    public String getEmail(){
        return email;
    }
}

public class Employees {
    private ArrayList<Employee> employees = new ArrayList<Employee>();

    public Employees(){
        employees.add(new Employee("John Smith", "johnsmith@email.com"));
    }

    public void addEmpNew (Employee empNew){
        employees.add(empNew);
    }
}

public class Session {
    private void addEmployee(){
        System.out.print("Name: ");
        String addEmpName = In.nextLine();

        System.out.print("Email: ");
        String addEmpEmail = In.nextLine();

        Employees v1 = new Employees();
        v1.addEmpNew(new Employee(addEmpName, addEmpEmail));
    }
}

But when I run it and put in the new employee and use a viewEmployees() method that shows all employees, It doesn't show the new one I added in, only showing the john smith one I pre-wrote in. I have a suspicion there may be something wrong with the addEmpNew method but I'm not sure.

Answer 1

You are creating an instance of Employees (called v1) within the addEmployee method. After the addEmployee method completes, all of the variables inside the method are gone (ready to be garbage collected).

If you are expecting to only have one instance of the Employees, consider making it a global variable.

public class Session {
    private final Employees v1 = new Employees();

    private void addEmployee(){
        System.out.print("Name: ");
        String addEmpName = In.nextLine();

        System.out.print("Email: ");
        String addEmpEmail = In.nextLine();

        v1.addEmpNew(new Employee(addEmpName, addEmpEmail));
    }

    private void printEmployees(){
        // you will have to implement the toString method in Employees class
        System.out.print("Employees: " + v1.toString());
    }
}