Object is null

[Pradeep Adibatla]

I have 2 classes A and B...

I want to use a HashMap(having get,set) of classA in classB...


This is what I did classB...

public ClassA classA;
public HashMap hashB;


function Use()
{
   hashB=classA.getHashA();  


}

classA is null...

what should be corrected in the above?

[Embla Tingeling]

Pradeep Adibatla wrote:
what should be corrected in the above?

public ClassA classA = new ClassA();   // assign object
public ClassB classB = new ClassB();   // assign object
public HashMap<ClassA,ClassB> hashB = new HashMap<ClassA,ClassB>();   // assign object
  
void use()  {   
   hashB.put(classA,classB); // store ClassB object in HashMap using ClassA key
   ClassB b = hashB.get(classA); // get it back
}  

You need to assign objects to the variables you declare, otherwise they will be null.

For this to work properly you most likely will have to override the equals and hashCode methods of ClassA.

[Pradeep Adibatla]

I have the hashmap ready in classA object..I need to use it here.. If I create with new it becomes a new Class A object and it's hashmap will contain nothing since it is a new object isn't it?

[Pradeep Adibatla]

Let me elaborate...

In classA, hash map ,say I have 3 records like empNo,Employee

Now I need to get 3 values in class B... This is what I require...

HashA =new HashA<String,Emloyee>

HashA.put("1",ABC);
HashB.put("2",XYZ);
HashC.put("3",LMN);


In CLassB:-->

If I do ClassA classA =new ClassA();

// This would mean a new object isn't it?

I have HashB=new HAshB<String,Employee>


I wrote...

HashB=classA.getHashA();