src/main/java/com/example/demo/service/HelloService.java

@@ -0,0 +1,21 @@
+package com.example.demo.service;
+
+import org.springframework.stereotype.Service;
+
+@Service
+public class HelloService {
+
+    private static final String GREETING_TEMPLATE = "Hello, %s!";
+    private static final String DEFAULT_GREETING = "Hello, World!";
+
+    public String getGreeting() {
+        return DEFAULT_GREETING;
+    }
+
+    public String getGreetingFor(String name) {
+        if (name == null || name.isBlank()) {
+            return DEFAULT_GREETING;
+        }
+        return String.format(GREETING_TEMPLATE, name);
+    }
+}