[Spring] Spring Data JPA

package com.luv2code.springboot.cruddemo.dao;

import com.luv2code.springboot.cruddemo.entity.Employee;
import java.util.List;

public interface EmployeeDAO {
    public List<Employee> findAll();

    public Employee findById (int theId);

    public void save(Employee theEmployee);

    public void deleteById(int theId);
}

package com.luv2code.springboot.cruddemo.dao;

        import com.luv2code.springboot.cruddemo.entity.Employee;
        import org.springframework.data.jpa.repository.JpaRepository;

public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
    // NO need to write any code here
}

package com.luv2code.springboot.cruddemo.service;

import com.luv2code.springboot.cruddemo.dao.EmployeeRepository;
import com.luv2code.springboot.cruddemo.entity.Employee;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.Optional;

public class EmployeeServiceImpl implements EmployeeService{

    private EmployeeRepository employeeRepository;

    @Autowired
    public EmployeeServiceImpl (EmployeeRepository theEmployeeRepository) {
        employeeRepository = theEmployeeRepository;
    }

    @Override
    public List<Employee> findAll() {
        return employeeRepository.findAll();
    }

    @Override
    public Employee findById(int theId) {

        Optional<Employee> result=  employeeRepository.findById(theId);
        Employee theEmployee = null;
        if (result.isPresent()) {
            theEmployee = result.get();
        } else {
            throw new RuntimeException("Did not find employee id  - " + theId);
        }

        return theEmployee;
    }

    @Override
    public void save(Employee theEmployee) {
        employeeRepository.save(theEmployee);
    }

    @Override
    public void deleteById(int theId) {
        employeeRepository.deleteById(theId);
    }
}