refactor student and logic

src/main/java/com/ebrains/cruddemo/service/StudentService.java

@@ -0,0 +1,11 @@
+package com.ebrains.cruddemo.service;
+
+import com.ebrains.cruddemo.entity.Student;
+import org.springframework.stereotype.Service;
+
+@Service
+public interface StudentService {
+    Student getStudentById(long id);
+    void saveStudent(Student student);
+    void deleteStudentById(long id);
+}