Implemented node repository

src/main/java/ru/dragonestia/loadbalancer/repository/NodeRepository.java

@@ -0,0 +1,17 @@
+package ru.dragonestia.loadbalancer.repository;
+
+import ru.dragonestia.loadbalancer.model.Node;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface NodeRepository {
+
+    void createNode(Node node);
+
+    void deleteNode(Node node);
+
+    Optional<Node> findNode(String nodeId);
+
+    List<Node> all();
+}

src/main/java/ru/dragonestia/loadbalancer/repository/impl/NodeRepositoryImpl.java

@@ -0,0 +1,46 @@
+package ru.dragonestia.loadbalancer.repository.impl;
+
+import ru.dragonestia.loadbalancer.model.Node;
+import ru.dragonestia.loadbalancer.repository.NodeRepository;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class NodeRepositoryImpl implements NodeRepository {
+
+    private final Map<String, Node> nodeMap = new ConcurrentHashMap<>();
+
+    @Override
+    public void createNode(Node node) {
+        synchronized (nodeMap) {
+            if (nodeMap.containsKey(node.identifier())) {
+                throw new IllegalArgumentException("Node with id '" + node.identifier() + "' already exists");
+            }
+
+            nodeMap.put(node.identifier(), node);
+        }
+    }
+
+    @Override
+    public void deleteNode(Node node) {
+        synchronized (nodeMap) {
+            nodeMap.remove(node.identifier());
+        }
+    }
+
+    @Override
+    public Optional<Node> findNode(String nodeId) {
+        synchronized (nodeMap) {
+            return nodeMap.containsKey(nodeId)? Optional.of(nodeMap.get(nodeId)) : Optional.empty();
+        }
+    }
+
+    @Override
+    public List<Node> all() {
+        synchronized (nodeMap) {
+            return nodeMap.values().stream().toList();
+        }
+    }
+}