第二次的作业

1. First program doesn't exist a state whose i = 0. Second program can only return first 0 in x.

2. x = null Expected = Null PointerException

   x = null Expected = Null PointerException

3. x = [2] Expected = -1

   x = [2] Expected = -1

4. x = [2, 3, 5] ; y = 5 Expected = 2

   x = [0, 1, 2] Expected = 0