fixed issue [#14]

src/main/java/io/github/pitzzahh/atm/dao/AtmDAOImplementation.java

@@ -1,8 +1,8 @@
 package io.github.pitzzahh.atm.dao;
 
-import java.sql.SQLException;
 import java.util.*;
 import javax.sql.DataSource;
+import java.sql.SQLException;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 import java.util.function.Function;
@@ -69,14 +69,20 @@ public Supplier<Map<String, Client>> getAllClients() {
      * <p>T - a {@code String} containing the account number to be search from the database.</p>
      * <p>R - a {@code Optional<Client>} containing the result if the client is found or not.</p>
      * @return a {@code Optional<Client>} object.
+     * @throws IllegalArgumentException if the account number does not belong to any client.
      * @see Function
-     * @see Optional
      * @see Client
      */
     @Override
-    public Function<String, Optional<Client>> getClientByAccountNumber() {
+    public Function<String, Client> getClientByAccountNumber() throws IllegalArgumentException {
         final var QUERY = "SELECT * FROM clients WHERE account_number = ?";
-        return an -> Optional.ofNullable(db.queryForObject(QUERY, new ClientMapper(), SecurityUtil.encrypt(an)));
+        return an -> {
+            try {
+                return db.queryForObject(QUERY, new ClientMapper(), SecurityUtil.encrypt(an));
+            } catch (RuntimeException ignored) {
+                throw new IllegalArgumentException(String.format("CLIENT WITH ACCOUNT NUMBER: %s DOES NOT EXIST", an));
+            }
+        };
     }
 
     /**
@@ -299,15 +305,16 @@ public Function<String, Integer> getLoanCount() {
      * Function that approves a loan request.
      * The function takes a {@code Loan} object containing the loan information to be approved.
      * @return a {@code Status} of the query wether {@link Status#SUCCESS} or {@link Status#ERROR}.
+     * @throws IllegalArgumentException if the account number does not belong to any client, thus the message cannot be found.
      * @see BiFunction
      * @see Loan
      * @see Status
      */
     @Override
-    public BiFunction<Loan, Client, Status> approveLoan() {
+    public BiFunction<Loan, Client, Status> approveLoan() throws IllegalArgumentException {
         final var QUERY = "UPDATE loans SET pending = ? WHERE loan_number = ? AND account_number = ?";
         return (loan, c) -> {
-            var client = getClientByAccountNumber().apply(c.accountNumber()).get();
+            var client = getClientByAccountNumber().apply(c.accountNumber());
             var status = updateClientSavingsByAccountNumber().apply(client.accountNumber(), client.savings() + loan.amount());
             return status == SUCCESS ? db.update(
                     QUERY,