Polymorphism and Abstract Classes - Absolute Java - page 503

Self-Test Exercises (continued)

8 . ★ What output is produced by the following code?

Sale someObject = new Sale("map", 5);
DiscountSale ds = new DiscountSale();
if (someObject instanceof DiscountSale)
{
ds = (DiscountSale)someObject;
System.out.println("ds was changed to " + someObject);
}
else

System.out.println("ds was not changed.");

★

9. Suppose we removed the qualifi er static from the method announcement()

in both Sale ( Display 8.1 ) and DiscountSale ( Display 8.2 ). What would
be the output produced by the following code (which is similar to the end of
Display 8.4 )?

Sale s = new Sale( );
DiscountSale discount = new DiscountSale( );
s.announcement( );
discount.announcement( );
System.out.println("No surprises so far, but wait.");
Sale discount2 = discount;
System.out.println(
"discount2 is a DiscountSale object in a Sale variable.");
System.out.println(
"Which definition of announcement( ) will it use?");
discount2.announcement( );
System.out.println(
"Did it use the Sale version of announcement()?");