feat: add money order feature for Davis lesson 17 with better organized code and all test passing

Author: DavisD251

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

@@ -6,7 +6,7 @@
 /** Represents a account. */
 abstract class BankAccount {
 
-  protected final Set<Customer> owners;
+  protected static Set<Customer> owners = null;
   protected final String accountNumber;
   protected double balance;
   protected boolean isActive;

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

@@ -5,7 +5,7 @@
 public class CheckingAccount extends BankAccount {
 
   /**
-   * Creates a new saving account.
+   * Creates a new checking account.
    *
    * @param accountNumber The account number.
    * @param owners The owners of the account.

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

@@ -0,0 +1,75 @@
+package com.codedifferently.lesson17.bank;
+
+/** Represents a money order. */
+public class MoneyOrder {
+
+  private final String orderNumber;
+  private final double amount;
+  private final BankAccount sourceAccount;
+  private boolean isRedeemed = false;
+
+  /**
+   * Creates a new money order and immediately withdraws funds.
+   *
+   * @param orderNumber The money order number.
+   * @param amount The amount of the money order.
+   * @param sourceAccount The account the money order is drawn from.
+   */
+  public MoneyOrder(String orderNumber, double amount, BankAccount sourceAccount) {
+    if (amount < 0) {
+      throw new IllegalArgumentException("Money order amount must be positive");
+    }
+    this.orderNumber = orderNumber;
+    this.amount = amount;
+    this.sourceAccount = sourceAccount;
+
+    // Immediately withdraw funds
+    sourceAccount.withdraw(amount);
+  }
+
+  /** Checks if the money order has already been redeemed. */
+  public boolean isRedeemed() {
+    return isRedeemed;
+  }
+
+  /**
+   * Redeems the money order to another account.
+   *
+   * @param toAccount The account receiving the funds.
+   */
+  public void redeem(BankAccount toAccount) {
+    if (isRedeemed) {
+      throw new IllegalStateException("Money order already redeemed");
+    }
+    toAccount.deposit(amount);
+    isRedeemed = true;
+  }
+
+  @Override
+  public int hashCode() {
+    return orderNumber.hashCode();
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (obj instanceof MoneyOrder other) {
+      return orderNumber.equals(other.orderNumber);
+    }
+    return false;
+  }
+
+  @Override
+  public String toString() {
+    return "MoneyOrder{"
+        + "orderNumber='"
+        + orderNumber
+        + '\''
+        + ", amount="
+        + amount
+        + ", sourceAccount="
+        + sourceAccount.getAccountNumber()
+        + ", redeemed="
+        + isRedeemed
+        + '}';
+  }
+}

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

@@ -0,0 +1,15 @@
+package com.codedifferently.lesson17.bank;
+
+/** A specialized type of BankAccount representing a source of funds. */
+public class SourceAccount extends BankAccount {
+
+  /**
+   * Constructs a SourceAccount with the given account number and initial balance.
+   *
+   * @param accountNumber The account number.
+   * @param initialBalance The starting balance.
+   */
+  public SourceAccount(String accountNumber, double initialBalance) {
+    super(accountNumber, owners, initialBalance);
+  }
+}

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

@@ -0,0 +1,15 @@
+package com.codedifferently.lesson17.bank;
+
+/** A specialized type of BankAccount representing a target (destination) for funds. */
+public class TargetAccount extends BankAccount {
+
+  /**
+   * Constructs a TargetAccount with the given account number and initial balance.
+   *
+   * @param accountNumber The account number.
+   * @param initialBalance The starting balance.
+   */
+  public TargetAccount(String accountNumber, double initialBalance) {
+    super(accountNumber, owners, initialBalance);
+  }
+}

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

@@ -0,0 +1,53 @@
+package com.codedifferently.lesson17.bank;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.codedifferently.lesson17.bank.exceptions.InsufficientFundsException;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class MoneyOrderTest {
+
+  private BankAccount sourceAccount;
+  private BankAccount targetAccount;
+
+  @BeforeEach
+  void setUp() {
+    sourceAccount = new SourceAccount("123", 500);
+    targetAccount = new TargetAccount("456", 100);
+  }
+
+  @Test
+  void testMoneyOrderWithdrawalOnCreation() {
+    new MoneyOrder("MO-001", 200, sourceAccount);
+    assertEquals(300, sourceAccount.getBalance(), 0.001);
+  }
+
+  @Test
+  void testMoneyOrderRedeem() {
+    MoneyOrder mo = new MoneyOrder("MO-002", 150, sourceAccount);
+    mo.redeem(targetAccount);
+
+    assertEquals(250, targetAccount.getBalance(), 0.001);
+    assertTrue(mo.isRedeemed());
+  }
+
+  @Test
+  void testRedeemAlreadyRedeemedMoneyOrderThrows() {
+    MoneyOrder mo = new MoneyOrder("MO-003", 100, sourceAccount);
+    mo.redeem(targetAccount);
+
+    IllegalStateException exception =
+        assertThrows(IllegalStateException.class, () -> mo.redeem(targetAccount));
+    assertEquals("Money order already redeemed", exception.getMessage());
+  }
+
+  @Test
+  void testInsufficientFundsOnCreation() {
+    BankAccount lowFundsAccount = new SourceAccount("789", 50);
+    assertThrows(
+        InsufficientFundsException.class, () -> new MoneyOrder("MO-004", 100, lowFundsAccount));
+  }
+}