SWE 437 In Class Exercise # 14
Input Space Partitioning

Instructions: Work with your neighbors in groups. This is an Input Space Partitioning exercise. It's #4 from exercises 6.2 (page 90). Consider the method intersection() below, along with a defective IDM:
public static Set intersection (Set s1, Set s2)
 * @param  s1, s2 : sets to compute intersection of
 * @return a (non null) Set equal to the intersection of Sets s1 and s2
 * @throws NullPointerException if s1 or s2 is null

Characteristic: Type of s1
- s1 = null
- s1 = {}
- s1 has at least one element

Characteristic: Relation between s1 and s2
- s1 and s2 represent the same set
- s1 is a subset of s2
- s2 is a subset of s1
- s1 and s2 do not have any elements in common