Deep Copy Constructor

[tngo]

I need some help in implementing deep copy constructor and not using the clone method. I understand that in order for the deep copy to work, you are making a copy of the object and not just the address pointing to that object. Otherwise if you make changes to one the original object will also observe the change. However, I am having problem with putting it into practice.

 /**
  * This is the main method.
  * It creates a Team object and then tests the copy constructor.
  */
  public static void main(String[] args)
   	{
		Team team1 = new Team("The Java Studs", "Bill", "Ted", "Carol", "Alice", 
					 new Competition("ACM Programming Contest","The Java Studs", "Team University Java", 2008),
					 new Competition("Antarctic Programming Contest","The Java Studs", "Frigid South", 2010) );
		Team team2 = new Team(team1);	// Copy constructor

		// Change competition information for team2
		team2.getCompetition1().setYear(2011);
		team2.getCompetition1().setWinner("Mmm Java");
		team2.getCompetition1().setRunnerup("Java By Night Java By Day");
		team2.getCompetition2().setYear(2012);

		// Output information for both team1 and team2.
		// Team1's should be unchanged from the original values.
		team1.OutputTeamInfo();
		team2.OutputTeamInfo();
	}

   	/**
	* Team copy constructor;  Performs a deep copy from the Competition class
	* instead of just copying a reference to the same Competition objects.
 	*/
 	public Team(Team otherTeam)
 	{
 		Team copyTeam = new Team();
 		copyTeam.setCompetition1(this.competition1);
 		copyTeam.setCompetition2(this.competition2);
 		copyTeam.setName1(this.name1);
 		copyTeam.setName2(this.name2);
 		copyTeam.setName3(this.name3);
 		copyTeam.setName4(this.name4);
 	
	}

This is my output from command line when I try to run it.

Exception in thread "main" java.lang.NullPointerException
at Team.main(Team.java:172)

[DarrylBurke]

You have things back-to-front in your copy constructor. You need to copy/set the attributes of the passed-in Team to the current instance ("this")

db

[tngo]

It could be that I need coffee this morning but could you help me understand this with an example? I tried fixing the codes but I feel that I'm only referencing the address because the changes are being observed by both team1 and team2.

[Tolls]

It's a constructor, not a clone() method, so there is no copyTeam object.
You need to do:

this.setCompetition1(otherTeam.competition1);
etc etc

That will give you a second Team object that references the same data that the original Team object references.