ArrayList and ensureCapacity, strange behavior

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If have following class:

class CapacityTrackingArrayList<T> extends ArrayList<T>
{
public boolean add(T elem)
{
    System.out.printf("Invoking add()... \n");
    boolean isAdded = super.add(elem);
    return isAdded;
}

public void ensureCapacity(int arg)
{
    System.out.printf("Invoking ensureCapacity(%d)... \n", arg);
    super.ensureCapacity(arg);
}
}  // class CapacityTrackingArrayList

and testing with...

CapacityTrackingArrayList<Integer> numberList2 = new CapacityTrackingArrayList<Integer>();
numberList2.ensureCapacity(100);
for (int i = 0; i <= 5; i++)
{
    numberList2.add(i);
}

I get following output

Invoking ensureCapacity(100)... 
Invoking ensureCapacity(1)... 
Invoking add()... 
Invoking ensureCapacity(2)... 
Invoking add()... 
Invoking ensureCapacity(3)... 
Invoking add()... 
Invoking ensureCapacity(4)... 
Invoking add()... 
Invoking ensureCapacity(5)... 

What strikes me is that, even though I call

numberList2.ensureCapacity(100);

before adding, I would expect the list to keep this capacity until about 100 elements have been added.

Apparently, not at all!

Always, when adding an element, it invokes ensureCapacity() ?? How come?

regards Chris

asked 45 secs ago

user2796195

36