Question

I need to clear the array list,Which one is better approach?Why?

Approach 1 :

List list = new ArrayList();
list.add("ram");

if(list!=null)
{
  list.clear();
}

Approach 2:

List list = new ArrayList();
list.add("ram");

if(list!=null && !list.isEmpty())
{
  list.clear();
}   

In the approach 1, I don’t check whether list is empty or not,directly i have been clear the list.

But in the approach 2, i have been clear the list if the list is not empty by checking

if(list!=null && !list.isEmpty())

Which one is better approach?Approach 1 or approach 2?

Answer 1

It depends on the implementation, for ArrayList for example (this is its clear method’s code):

     public void clear() {
         modCount++;

         // Let gc do its work
         for (int i = 0; i < size; i++)
             elementData[i] = null;

         size = 0;
     }

Means that the code doesn’t spend more time if the list is already empty. In this sense I would just clear the code as you did with the first approach.