Homework 5

• Exercise 15.x1: One can show the subtype relation on Java types by drawing a diagram with arrows, where each arrow points from a subtype to one of its supertypes. Arrows can be omitted that are implied by transitivity. As a simple example, if the types under consideration are Integer, Number, and Object, one would draw an arrow pointing from Integer to Number and a second arrow pointing from Number to Object, but there would be no need to show an arrow from Integer directly to Object. Using this diagramming convention, show the subtyping relation on List<?>, ArrayList<?>, List<Number>, ArrayList<Number>, List<Integer>, and ArrayList<Integer>.

• Do exercise 16.3 on page 315-316. Assume that the interfaces are defined as follows:

  interface I1 {};
  interface I2 {};