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

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

@@ -0,0 +1,80 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.dao;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/**
+ * 
+ * The data access object (DAO) is an object that provides an abstract interface to some type of
+ * database or other persistence mechanism. By mapping application calls to the persistence layer,
+ * DAO provide some specific data operations without exposing details of the database. This
+ * isolation supports the Single responsibility principle. It separates what data accesses the
+ * application needs, in terms of domain-specific objects and data types (the public interface of
+ * the DAO), from how these needs can be satisfied with a specific DBMS, database schema, etc.
+ * 
+ */
+// TODO update the javadoc
+public class InMemoryCustomerDao implements CustomerDao {
+
+  private Map<Integer, Customer> idToCustomer = new HashMap<>();
+
+  public InMemoryCustomerDao(final List<Customer> customers) {
+    customers.stream()
+    .forEach((customer) -> idToCustomer.put(customer.getId(), customer));
+  }
+
+  @Override
+  public Stream<Customer> getAll() {
+    return idToCustomer.values().stream();
+  }
+
+  @Override
+  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 boolean update(final Customer customer) {
+    return idToCustomer.replace(customer.getId(), customer) != null;
+  }
+
+  @Override
+  public boolean delete(final Customer customer) {
+    return idToCustomer.remove(customer.getId()) != null;
+  }
+}