1.
> IntSeq u = new IntSeq(new int[] {1, -3, 5, -7, 4}); 
a)
> u.m1()
35
b)
> u.m2(u)
100
c)
> u.m3()
12
d)
> u.m4()
3

2.
> I[] a = {new I("A", 2), new J("B", 2, .1), new K("C", 2, 10, .2)}; 
a)
> a[0].m(15)
30.0
b)
> a[1]
BJ
c)
> a[1].m(15)
27.0
d)
> a[2].m(15)
26.0

3.

(a) Ticket t1 = new Ticket();                           OK
(b) t1.setCurrentPrice(10);                             OK
(c) Ticket t2 = new Ticket();                           OK
(d) t1.getPrice()                                      5.0
(e) Ticket.revenue                                   error
(f) Ticket[] ts = new Ticket[10];                       OK
(g) for (int i = 0; i < 10; i++) ts[i] = new Ticket();  OK
(h) Ticket.getIssued()                                  12

4.

a)
  public void rotate() {
    if (size() < 2) return;
    int tmp = data[0];
    for (int i = 1; i < size(); i++) data[i-1] = data[i];
    data[size()-1] = tmp;
  }

b)
  public void truncate(int pos) {
    int newSize = pos;
    int[] newData = new int[newSize];
    for (int i = 0; i < newSize; i++)
      newData[i] = data[i];
    data = newData;
  }

c)
  public void splice(int from, int to, IntSeq mid) {
    int[] newData = new int[from + mid.size() + size() - to];
    int j = 0;
    for (int i = 0; i < from; i++) newData[j++] = data[i];
    for (int i = 0; i < mid.size(); i++) newData[j++] = mid.get(i);
    for (int i = to; i < size(); i++) newData[j++] = data[i];
    data = newData;
  }

5.

a)

(i)        normal 
(ii)       error 
(iii)      error 
(iv)       normal 

b)

public class Ring implements Displaceable, Area {
  private Circle inner, outer;
  public Ring(Point center, double radius, double width) {
    inner = new Circle(center, rad);
    outer = new Circle(center, rad + width);
  }
  public double getX() { return inner.getX(); }
  public double getY() { return inner.getY(); }
  public double getArea() { return outer.getArea() - inner.getArea(); }
  public void move(double dx, double dy) {
    inner.move(dx, dy);
  }
}