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>.
Exercise 17.x1: For each of the following two Java statements, indicate whether it is legal, and if so, explain under what circumstances each exception handler would execute. The first version is
try {
System.in.read();
} catch(java.io.CharConversionException e2){
System.err.println("Caught a CharConversionException.");
} catch(java.io.IOException e1){
System.err.println("Caught an IOException.");
}
and the second version is
try {
System.in.read();
} catch(java.io.IOException e1){
System.err.println("Caught an IOException.");
} catch(java.io.CharConversionException e2){
System.err.println("Caught a CharConversionException.");
}
Do exercise 18.6 on page 381.