Consider the following code snippet:
public class SavingsAccount extends BankAccount { ...}
public class CheckingAccount extends BankAccount { ...}
...
SavingsAccount[] savingsAccounts = new SavingsAccount[100]; //Line 1
BankAccount[] bankAccounts = savingsAccounts; //Line 2
BankAccount myAccount = new CheckingAccount(); //Line 3
bankAccounts[0] = myAccount; //Line 4
Which of the following statements regarding this code is correct?
A)Line 2 will cause a run-time error.
B)Line 4 will cause a compile-time error.
C)Line 4 will cause a run-time error.
D)Line 2 will cause a compile-time error.

Question

Quizplus · Accepted Answer

Line 2 is valid because a SavingsAccount is a type of BankAccount, therefore a SavingsAccount array can be cast to a BankAccount array. 
Line 4 is where the issue occurs. Since bankAccounts was declared as a BankAccount array but was assigned a SavingsAccount array, it is possible to assign a CheckingAccount to an element in the array. However, since bankAccounts is referencing a SavingsAccount array, a run-time error will occur when a CheckingAccount is assigned to it because the CheckingAccount is not of type SavingsAccount.

Consider the Following Code Snippet