How to create an array of ArrayLists in java?

Question

I am creating an array but cannot add values to it.

ArrayList<SMS>[] lists = (ArrayList<SMS>[])new ArrayList[count];

        for(int i=0;i<temp.size();i++)
        {
            String number="",id="";
            number = temp.get(i).addr;
            id = temp.get(i).thread_id;
            lists[i].add(temp.get(i));            // Problem here
        }

I am unable to add value to it

You have to actually create the individual ArrayList objects. The new ArrayList[count] operation only creates the array itself. — Hot Licks
– Hot Licks, Commented Mar 30, 2014 at 17:52

Thomas · Accepted Answer · 2014-03-30 17:53:09Z

4

You're creating an array of null references, so you need to initialize each of them to a new ArrayList<SMS>():

for (int i = 0; i < count; i++) {
    lists[i] = new ArrayList<SMS>();
}

answered Mar 30, 2014 at 17:53

Thomas

183k57 gold badges383 silver badges510 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Thalaivar · Accepted Answer · 2014-03-30 17:54:02Z

2

int size = 9;
ArrayList<SMS>[] lists = new ArrayList[size];
for( int i = 0; i < size; i++) {
    lists[i] = new ArrayList<SMS>();
}

answered Mar 30, 2014 at 17:54

Thalaivar

23.7k5 gold badges63 silver badges71 bronze badges

Collectives™ on Stack Overflow

How to create an array of ArrayLists in java?

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related