Hints for Lab 5

To check if a variable points to an object of a certain class you can use the operator instanceof. For example, to check if newAcc points to an object of the class CheckingAccount you could use if (newAcc instanceof CheckingAccount) .

Remember that if a variable of a certain class C is pointing to an object of a subclass of C, the compiler will issue compilation errors if a method of the subclass is invoked. For example, if newAcc is of type BankAccount and it points to an object of the class CheckingAccount, then the compiler will print an error message with this statement newAcc.getTransactionCount() because method getTransactionCount() has not been defined in class BankAccount. To fix the error you must use casting: Cast the variable newAcc to type CheckingAccount (((CheckingAccount)newAcc).getTransactionCount()).