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Exercise 7.7
Static and dynamic types

Type conversion with v as T was illustrated with a program on the accompanying slide. The output of the program was confusing and misleading. We want to report the static types of the expressions ba1 as BankAccount, ba1 as CheckAccount, etc. If you access this exercise from the web-version there will be direct links to the appropriate pieces of program.

Explain the output of the program. You can examine the classes BankAccount, CheckAccount, SavingsAccount and LotteryAccount, if you need it.

Modify the program such that the static type of the expressions bai as BanktypeAccount is reported. Instead of

  baRes1 = ba1 as BankAccount; 

you should activate some method on the expression ba1 as BankAccount which reveals its static type. In order to do so, it is allowed to add extra methods to the bank account classes.