adding new lists to a 2d array

Question

I have a 2d array

ArrayList<List<Customer>> list;

Each customerNode stores two customers. I want to add a new list of customers to the list array if neither of the customers exist in any of the current List<Customer> in list. However, when I run this it doesnt add the 'newR' to the list.

for(customerNode s: customers){
    count++;
    if(!LinearSearch2(s.getOne(), s.getTwo())){
        System.out.println("Test");
        ArrayList<Customer> newR = new ArrayList<Customer>();
        newR.add(s.getOne());
        newR.add(s.getTwo());
        list.add(newR);
    }
}

thanks in advance!

Mena · Accepted Answer · 2015-10-23 11:00:16Z

2

This is your problem:

List<Customer> newR = null;
newR.add(s.getOne());

You need to initialize newR by assigning it a new instance of List, such as new ArrayList<Customer>();.

Otherwise, your newR reference is pointing to null and you can't invoke methods on it without the JVM throwing a NullPointerException.

answered Oct 23, 2015 at 11:00

Mena

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1 Comment

Darth123 Over a year ago

I just realised that as soon as I posted, the problem is that it still doesn't add the 'newR' to my list, although I am not given any errors

Darth123 · Accepted Answer · 2015-10-23 11:15:54Z

0

Fixed: the problem was with a loop elsewhere in my code

answered Oct 23, 2015 at 11:15

Darth123

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