#1 is patially true
ArrayList can store elements that are Objects. So any reference to a type Object can be directly stored. A primitive like int can be still be store provided its converted to an object. Ex. Integer. ArrayList can also store a null.
#2 True.
Much cannot be explained about this. The definition of ArrayList is like:
public class ArrayList extends AbstractList implements List, RandomAccess, Cloneable, Serializable #3 True
Refer to the API...
http://java.sun.com/j2se/1.4.2/docs/api/ #4 Definetely elements are not sorted in an ArrayList.
Only in TreeSet and TreeMap elements are stored in the ascending order. Both TreeSet and TreeMap implement the SortedSet and the SortedMap interfaces. ArrayList implements only the List interface hence the elements are not automatically stored in the sorted order.
Hope this helps!!
- Mel