Why java does not autobox int[] to Integer[]

Question

When I do the following,

• arrayList1 - contains one element and it is an int[].
• arrayList2 - not compiling (Err

Answer 1

arrayList1 is really a List of size one.

http://ideone.com/w0b1vY

arrayList1.size() = 1
arrayList3.size() = 7

The int[] is being cast to a single Object. That Object cannot be cast to Integer.