nullpointerexception for array of objects

Question

I have the following test class

public class Driver
{
    public static void main(String [] args)
        {
             BankAccount[] b1 = {new BankAccount(200), new BankAccount(300), new BankAccount(250), new BankAccount(300), new BankAccount(200)};
              BankAccountGroup bag = new BankAccountGroup(b1);                      

        }

And BankAccountGroup:

public class BankAccountGroup 
{ 
private BankAccount bank[];
public BankAccountGroup(BankAccount[]b)
{
for(int i =0; i<5;i++)
{
bank[i] = b[i];
}
}

these are just snippets of the whole code. Im getting a nullpointerexception for these two lines: - bank[i] = b[i]; - BankAccountGroup bag = new BankAccountGroup(b1); Please help

Umibozu · Accepted Answer · 2015-09-25 22:38:02Z

1

When you declare bank[] in the BankAccountGroup class it looks like you forgot to give it a length. Because of this, when you call bank[i] in your for loop, anything after i=0 is probably going to give you an error.

something like

private BankAccount[] bank = new BankAccount[5];

edited Sep 25, 2015 at 22:38

answered Sep 25, 2015 at 22:32

Umibozu

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1 Comment

Umibozu Over a year ago

Can you mark this as the answer? IMTRYINGTOGETSOMEPOINTS.

shad · Accepted Answer · 2015-09-25 23:54:06Z

1

Either initialize your array first(Bad).

Or assign it from the value you pass the constructor.

private BankAccount[] bank;
public BankAccountGroup(BankAccount []){
       bank = b;
}

answered Sep 25, 2015 at 23:54

shad

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Comments

user2509314 · Accepted Answer · 2015-09-25 22:49:36Z

0

You are not initializing the bank array. You also shouldn't assume that the argument will have a length of 5 elements. I would rewrite the class to something like this:

 public class BankAccountGroup 
{ 
    private BankAccount bank[];

    public BankAccountGroup(BankAccount[]b)
    {
        if (b != null)
        {
            bank = new BankAccount[b.length];

            for(int i=0; i<b.length;i++)
            {
                bank[i] = b[i];
            }
        }
    }
}

edited Sep 25, 2015 at 22:49

answered Sep 25, 2015 at 22:42

user2509314

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