Solved

Constructor

Posted on 2004-10-10
10
149 Views
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?



0
Comment
Question by:jtcy
  • 4
  • 2
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).
0
 
LVL 24

Accepted Solution

by:
sciuriware earned 30 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().....

0
Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

 
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

<*>
0

Featured Post

Back Up Your Microsoft Windows Server®

Back up all your Microsoft Windows Server – on-premises, in remote locations, in private and hybrid clouds. Your entire Windows Server will be backed up in one easy step with patented, block-level disk imaging. We achieve RTOs (recovery time objectives) as low as 15 seconds.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Introduction Java can be integrated with native programs using an interface called JNI(Java Native Interface). Native programs are programs which can directly run on the processor. JNI is simply a naming and calling convention so that the JVM (Java…
Introduction This article is the second of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers the basic installation and configuration of the test automation tools used by…
Viewers learn about the “while” loop and how to utilize it correctly in Java. Additionally, viewers begin exploring how to include conditional statements within a while loop and avoid an endless loop. Define While Loop: Basic Example: Explanatio…
Video by: Michael
Viewers learn about how to reduce the potential repetitiveness of coding in main by developing methods to perform specific tasks for their program. Additionally, objects are introduced for the purpose of learning how to call methods in Java. Define …

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question