如何区分一个类的两个实例

Question

I have two constructors of a class Transactions where they differ in the last argument where the first constructor takes a Label object and the second a Box object.

public class Transactions {
    private String date;
    private String kind;
    private int employee;
    private Label label;
    private Box box;

public Transactions(String date, String kind, int employee, Box box) {
    this.date = date;
    this.kind = kind;
    this.employee = employee;
    this.box = box;
}

public Transactions(String date, String kind, int employee, Label label) {
    this.date = date;
    this.kind = kind;
    this.employee = employee;
    this.label = label;
}


 ...

}

Lets say I have created an object of class Transactions which is tr . How can I distinguish which one is it? The one with the Label object or the one with the Box object? Which constructor has been called?

Answer 1

If you need to distinguish that, both objects probably should not be of the same class.

In your example, both classes could share a common superclass, or they should have a field of a special type, holding the common information.

Answer 2

You can easily check which one has just been called by checking if this.label == null .

You can also add a flag which would point which constructor has been called.

Anyway. If you are facing such a problem, you should definitely think out your code again. Those constructors probably shouldn't construct objects of the same class. Maybe some inheritance, maybe some composition...