feat: implement Account interface for polymorphism

- Add Account interface with core banking operations
- Update CheckingAccount to implement Account interface
- Modify BankAtm to work with Account interface instead of CheckingAccount
- Update Customer class to store Account objects
- Update Check class to work with Account interface
- Update tests to use Account interface
- All existing functionality preserved with 27 tests passing

Author: jmckellar252-png

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Account.java

@@ -0,0 +1,53 @@
+package com.codedifferently.lesson17.bank;
+
+import com.codedifferently.lesson17.bank.exceptions.InsufficientFundsException;
+import java.util.Set;
+
+/** Interface representing a bank account. */
+public interface Account {
+  /**
+   * Gets the account number.
+   *
+   * @return The account number.
+   */
+  String getAccountNumber();
+
+  /**
+   * Gets the owners of the account.
+   *
+   * @return The owners of the account.
+   */
+  Set<Customer> getOwners();
+
+  /**
+   * Deposits funds into the account.
+   *
+   * @param amount The amount to deposit.
+   */
+  void deposit(double amount);
+
+  /**
+   * Withdraws funds from the account.
+   *
+   * @param amount The amount to withdraw.
+   * @throws InsufficientFundsException If insufficient funds.
+   */
+  void withdraw(double amount) throws InsufficientFundsException;
+
+  /**
+   * Gets the balance of the account.
+   *
+   * @return The balance of the account.
+   */
+  double getBalance();
+
+  /** Closes the account. */
+  void closeAccount();
+
+  /**
+   * Checks if the account is closed.
+   *
+   * @return True if the account is closed, otherwise false.
+   */
+  boolean isClosed();
+}

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BankAtm.java

@@ -10,14 +10,14 @@
 public class BankAtm {
 
   private final Map<UUID, Customer> customerById = new HashMap<>();
-  private final Map<String, CheckingAccount> accountByNumber = new HashMap<>();
+  private final Map<String, Account> accountByNumber = new HashMap<>();
 
   /**
    * Adds a checking account to the bank.
    *
    * @param account The account to add.
    */
-  public void addAccount(CheckingAccount account) {
+  public void addAccount(Account account) {
     accountByNumber.put(account.getAccountNumber(), account);
     account
         .getOwners()
@@ -33,7 +33,7 @@ public void addAccount(CheckingAccount account) {
    * @param customerId The ID of the customer.
    * @return The unique set of accounts owned by the customer.
    */
-  public Set<CheckingAccount> findAccountsByCustomerId(UUID customerId) {
+  public Set<Account> findAccountsByCustomerId(UUID customerId) {
     return customerById.containsKey(customerId)
         ? customerById.get(customerId).getAccounts()
         : Set.of();
@@ -46,7 +46,7 @@ public Set<CheckingAccount> findAccountsByCustomerId(UUID customerId) {
    * @param amount The amount to deposit.
    */
   public void depositFunds(String accountNumber, double amount) {
-    CheckingAccount account = getAccountOrThrow(accountNumber);
+    Account account = getAccountOrThrow(accountNumber);
     account.deposit(amount);
   }
 
@@ -57,7 +57,7 @@ public void depositFunds(String accountNumber, double amount) {
    * @param check The check to deposit.
    */
   public void depositFunds(String accountNumber, Check check) {
-    CheckingAccount account = getAccountOrThrow(accountNumber);
+    Account account = getAccountOrThrow(accountNumber);
     check.depositFunds(account);
   }
 
@@ -68,7 +68,7 @@ public void depositFunds(String accountNumber, Check check) {
    * @param amount
    */
   public void withdrawFunds(String accountNumber, double amount) {
-    CheckingAccount account = getAccountOrThrow(accountNumber);
+    Account account = getAccountOrThrow(accountNumber);
     account.withdraw(amount);
   }
 
@@ -78,8 +78,8 @@ public void withdrawFunds(String accountNumber, double amount) {
    * @param accountNumber The account number.
    * @return The account.
    */
-  private CheckingAccount getAccountOrThrow(String accountNumber) {
-    CheckingAccount account = accountByNumber.get(accountNumber);
+  private Account getAccountOrThrow(String accountNumber) {
+    Account account = accountByNumber.get(accountNumber);
     if (account == null || account.isClosed()) {
       throw new AccountNotFoundException("Account not found");
     }

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Check.java

@@ -7,7 +7,7 @@ public class Check {
 
   private final String checkNumber;
   private final double amount;
-  private final CheckingAccount account;
+  private final Account account;
   private boolean isVoided = false;
 
   /**
@@ -17,7 +17,7 @@ public class Check {
    * @param amount The amount of the check.
    * @param account The account the check is drawn on.
    */
-  public Check(String checkNumber, double amount, CheckingAccount account) {
+  public Check(String checkNumber, double amount, Account account) {
     if (amount < 0) {
       throw new IllegalArgumentException("Check amount must be positive");
     }
@@ -45,7 +45,7 @@ public void voidCheck() {
    *
    * @param toAccount The account to deposit the check into.
    */
-  public void depositFunds(CheckingAccount toAccount) {
+  public void depositFunds(Account toAccount) {
     if (isVoided) {
       throw new CheckVoidedException("Check is voided");
     }

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/CheckingAccount.java

@@ -4,7 +4,7 @@
 import java.util.Set;
 
 /** Represents a checking account. */
-public class CheckingAccount {
+public class CheckingAccount implements Account {
 
   private final Set<Customer> owners;
   private final String accountNumber;

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Customer.java

@@ -9,7 +9,7 @@ public class Customer {
 
   private final UUID id;
   private final String name;
-  private final Set<CheckingAccount> accounts = new HashSet<>();
+  private final Set<Account> accounts = new HashSet<>();
 
   /**
    * Creates a new customer.
@@ -45,7 +45,7 @@ public String getName() {
    *
    * @param account The account to add.
    */
-  public void addAccount(CheckingAccount account) {
+  public void addAccount(Account account) {
     accounts.add(account);
   }
 
@@ -54,7 +54,7 @@ public void addAccount(CheckingAccount account) {
    *
    * @return The unique set of accounts owned by the customer.
    */
-  public Set<CheckingAccount> getAccounts() {
+  public Set<Account> getAccounts() {
     return accounts;
   }
 

lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/BankAtmTest.java

@@ -43,14 +43,14 @@ void testAddAccount() {
     classUnderTest.addAccount(account3);
 
     // Assert
-    Set<CheckingAccount> accounts = classUnderTest.findAccountsByCustomerId(customer3.getId());
+    Set<Account> accounts = classUnderTest.findAccountsByCustomerId(customer3.getId());
     assertThat(accounts).containsOnly(account3);
   }
 
   @Test
   void testFindAccountsByCustomerId() {
     // Act
-    Set<CheckingAccount> accounts = classUnderTest.findAccountsByCustomerId(customer1.getId());
+    Set<Account> accounts = classUnderTest.findAccountsByCustomerId(customer1.getId());
 
     // Assert
     assertThat(accounts).containsOnly(account1, account2);