Copy constructor create garbage objects

Question

My teacher gave me 2 classes, one is passport and the other is date.
date contain 3 attributes (string day,string month, string year), getters, setters and 2 constructors, one of them is a copy constructor:

 public date(date dt)
 this.day=dt.getd();
 this.month=dt.getm();
 this.yaer=dt.gety();

passport class contain 2 attributes (string name, date exp(from date class))and there is this construcor:

public passport(string name, date exp)   
this.name=name;  
this.exp= new date(exp);    

now in the main class, every time i create new date and new passport, every date is duplicate and i get 1 garbage object for every passport.
how can i get over this garbage object?

Answer 1

how can i get over this garbage object?

If date instances are mutable, you don't; you do what you're doing.

if date instances are immutable (their state cannot be changed once they've been created), then you just use the instance you're given rather than creating a new one:

public passport(string name, date exp)   
    this.name = name;  
    this.exp = exp;
}

You wouldn't want to do that if exp could be modified, because it would create cross-talk between your passport instance and whatever passed the exp to it.

Answer 2

how can i get over this garbage object?

Let the garbage collector does its job : as the Date variable passed as parameter to the Passport constructor will be out of scope of the execution context, the underlying Date object will be eligible to be collected.

The way the most straight to do it is to not assign the Date object to a variable.
Just inline its instantiation in the Passport constructor invocation :

Passport passport = new Passport(name, new Date(day, month, year));

Answer 3

optional solution:

in the main class:

passport[] arr = new passport[100];   // we have 100 passports
date d1= new date ()                  //null date
for (int i=0,i<100,i++)               // we have 100 passports
{ d1.setd();                          //our setter asks for an input
  d1.setm();
  d1.sety();
  arr [i]=new passport (string name, d1); }