Refactoring changes to DAO pattern. Renamed default dao implementation to InMemory and refined interface

dao/src/main/java/com/iluwatar/dao/App.java

@@ -51,18 +51,18 @@ public class App {
    * @param args command line args.
    */
   public static void main(final String[] args) {
-    final CustomerDao customerDao = new CustomerDaoImpl(generateSampleCustomers());
-    log.info("customerDao.getAllCustomers(): " + customerDao.getAllCustomers());
-    log.info("customerDao.getCusterById(2): " + customerDao.getCustomerById(2));
+    final CustomerDao customerDao = new InMemoryCustomerDao(generateSampleCustomers());
+    log.info("customerDao.getAllCustomers(): " + customerDao.getAll());
+    log.info("customerDao.getCusterById(2): " + customerDao.getById(2));
     final Customer customer = new Customer(4, "Dan", "Danson");
-    customerDao.addCustomer(customer);
-    log.info("customerDao.getAllCustomers(): " + customerDao.getAllCustomers());
+    customerDao.add(customer);
+    log.info("customerDao.getAllCustomers(): " + customerDao.getAll());
     customer.setFirstName("Daniel");
     customer.setLastName("Danielson");
-    customerDao.updateCustomer(customer);
-    log.info("customerDao.getAllCustomers(): " + customerDao.getAllCustomers());
-    customerDao.deleteCustomer(customer);
-    log.info("customerDao.getAllCustomers(): " + customerDao.getAllCustomers());
+    customerDao.update(customer);
+    log.info("customerDao.getAllCustomers(): " + customerDao.getAll());
+    customerDao.delete(customer);
+    log.info("customerDao.getAllCustomers(): " + customerDao.getAll());
   }
 
   /**

dao/src/main/java/com/iluwatar/dao/CustomerDao.java

@@ -22,7 +22,7 @@
  */
 package com.iluwatar.dao;
 
-import java.util.List;
+import java.util.stream.Stream;
 
 /**
  * 
@@ -31,13 +31,13 @@ import java.util.List;
  */
 public interface CustomerDao {
 
-  List<Customer> getAllCustomers();
+  Stream<Customer> getAll();
 
-  Customer getCustomerById(int id);
+  Customer getById(int id);
 
-  void addCustomer(Customer customer);
+  boolean add(Customer customer);
 
-  void updateCustomer(Customer customer);
+  boolean update(Customer customer);
 
-  void deleteCustomer(Customer customer);
+  boolean delete(Customer customer);
 }

dao/src/main/java/com/iluwatar/dao/DBCustomerDao.java

@@ -0,0 +1,38 @@
+package com.iluwatar.dao;
+
+import java.util.stream.Stream;
+
+public class DBCustomerDao implements CustomerDao {
+
+  @Override
+  public Stream<Customer> getAll() {
+    // TODO Auto-generated method stub
+    return null;
+  }
+
+  @Override
+  public Customer getById(int id) {
+    // TODO Auto-generated method stub
+    return null;
+  }
+
+  @Override
+  public boolean add(Customer customer) {
+    // TODO Auto-generated method stub
+    return false;
+  }
+
+  @Override
+  public boolean update(Customer customer) {
+    // TODO Auto-generated method stub
+    return false;
+  }
+
+  @Override
+  public boolean delete(Customer customer) {
+    // TODO Auto-generated method stub
+    return false;
+  }
+
+
+}

dao/src/main/java/com/iluwatar/dao/InMemoryCustomerDao.java

@@ -22,7 +22,10 @@
  */
 package com.iluwatar.dao;
 
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
 
 /**
  * 
@@ -34,51 +37,44 @@ import java.util.List;
  * the DAO), from how these needs can be satisfied with a specific DBMS, database schema, etc.
  * 
  */
-public class CustomerDaoImpl implements CustomerDao {
+// TODO update the javadoc
+public class InMemoryCustomerDao implements CustomerDao {
 
-  // Represents the DB structure for our example so we don't have to managed it ourselves
-  // Note: Normally this would be in the form of an actual database and not part of the Dao Impl.
-  private List<Customer> customers;
+  private Map<Integer, Customer> idToCustomer = new HashMap<>();
 
-  public CustomerDaoImpl(final List<Customer> customers) {
-    this.customers = customers;
+  public InMemoryCustomerDao(final List<Customer> customers) {
+    customers.stream()
+    .forEach((customer) -> idToCustomer.put(customer.getId(), customer));
   }
 
   @Override
-  public List<Customer> getAllCustomers() {
-    return customers;
+  public Stream<Customer> getAll() {
+    return idToCustomer.values().stream();
   }
 
   @Override
-  public Customer getCustomerById(final int id) {
-    Customer customer = null;
-    for (final Customer cus : getAllCustomers()) {
-      if (cus.getId() == id) {
-        customer = cus;
-        break;
-      }
-    }
-    return customer;
-  }
-
-  @Override
-  public void addCustomer(final Customer customer) {
-    if (getCustomerById(customer.getId()) == null) {
-      customers.add(customer);
+  public Customer getById(final int id) {
+    return idToCustomer.get(id);
+  }
+
+  @Override
+  public boolean add(final Customer customer) {
+    if (getById(customer.getId()) != null) {
+      return false;
     }
+    
+    idToCustomer.put(customer.getId(), customer);
+    return true;
   }
 
 
   @Override
-  public void updateCustomer(final Customer customer) {
-    if (getAllCustomers().contains(customer)) {
-      final int index = getAllCustomers().indexOf(customer);
-      getAllCustomers().set(index, customer);
-    }
+  public boolean update(final Customer customer) {
+    return idToCustomer.replace(customer.getId(), customer) != null;
   }
 
   @Override
-  public void deleteCustomer(final Customer customer) {
-    getAllCustomers().remove(customer);
+  public boolean delete(final Customer customer) {
+    return idToCustomer.remove(customer.getId()) != null;
   }
 }