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Constructor

Posted on 2004-10-10
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Last Modified: 2010-03-31
Can somebody tell me whats wrong with the following class?

--------------------------------------------------------------
public class Account
 {
       private Key myKey;
       private String username;
       private String password;
       
       public Account(Chat serverRef, String user, String pass)
        {
           myKey = new Key(serverRef);
           username = user;
           password = pass;
        }
       
       public Account(Chat serverRef)
        {
              myKey = null;
              username = null;
              password = null;
        }
       
       public String getUsername()
        {
              return username;
        }
   
    public String getPassword()
     {
           return password;
     }
   
    public Key getKey()
     {
           return myKey;
     }
   
 
     
 }
--------------------------------------------------------

The problem is, I do smth like:

Account myAccount = new Account(aChatServerObject, myUsername, myPassword); // it is fine but not until I do:

Key temp = myAccount.getKey(); // then it returns java.lang.nullpointerException. Why is that??? I cant see whats wrong with that though~~~ Somebody?



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Question by:jtcy
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10 Comments
 
LVL 21

Expert Comment

by:MogalManic
ID: 12270217
Make sure you are not calling the
   public Account(Chat serverRef)
constructor.  That constructor does NOT initialize the key field (though it probabyl should).
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LVL 24

Accepted Solution

by:
sciuriware earned 120 total points
ID: 12271467
In other words: when you use the short (overloaded) constructor, you should be prepared that:
1) .getKey() returns a null value, or,
2) .getKey() is smart enough to return a substitute value when null, or,
3) the shorter constructor is smart enough to set the internal field 'myKey' to a useful value.

The chosen default value depends on the rest of the use of this class.

;JOOP!
0
 
LVL 2

Expert Comment

by:ThummalaRaghuveer
ID: 12273323
I guess Account is not getting instantiated......

even if .getKey() returns null value all that happens is temp becomes null.......

Can you call any other methods in Account  like .getUserName().....

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LVL 24

Expert Comment

by:sciuriware
ID: 12274260
Nonsense! If  the constructor returns it carries a reference to an object!

So, Account is instantiated. You might verify this by:
    System.out.println("Instance = " + myAccount.toString());
printing the object address.
;JOOP!
0
 
LVL 2

Expert Comment

by:ThummalaRaghuveer
ID: 12291294
He gets such an exception only if myAccount is pointing to null at the time of calling getKey method on myAccount
0
 
LVL 24

Expert Comment

by:sciuriware
ID: 12298580
Right!

;JOOP!
0
 
LVL 24

Expert Comment

by:sciuriware
ID: 12542796
I believe my answer was right and verbose enough for A

<*>
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