ArrayList and IndexOutOfBoundsException

[Sanjeev Singh]

I was trying to execute the the Program

public class ArrayListTest {
    
    public static void main(String args[]){
        //iterating a list
        List li = new ArrayList();
        li.add("A");
        li.add("B");
        li.add("C");
        li.add("D");
        li.add(5,"E");
        ListIterator liIt = li.listIterator();
        while(liIt.hasNext()){
            System.out.println(liIt.next());
        }
    }
}

I got IndexOutOfBoundsException .
Does this means that the dynamic growing of the ArrayList doesnot happen when we add an element using indexes?

When I reexecuted with the initial capacity =10 ,got the same exception.

List li = new ArrayList(10);

So what initialCapacity is doing in the constructor of ArrayList?
[ December 17, 2006: Message edited by: Sanjeev Kumar Singh ]

[Joe Harry]

Sanjeev,

I works when you say 4, "E" instead of 5. Any reason behind this behavior to throw an exception??

[Joe Harry]

I think the code below will help you.

This is the add method as defined,

public void add(int index, E element) {
if (index > size || index < 0)
    throw new IndexOutOfBoundsException(
"Index: "+index+", Size: "+size);
 
ensureCapacity(size+1);  // Increments modCount!!
System.arraycopy(elementData, index, elementData, index + 1,
 size - index);
elementData[index] = element;
size++;
    }

Hope, now you can see why your code throws the exception. Hope this helped.