我有两个类，一个是Course，另一个是CourseController。它们在同一个包中，同一个路径;但是当我编译javac www.example.com时CourseController.java，Intellij说：“错误：找不到符号”
课程：

package com.mjfirstSBv5.sprintboot.learnspringboot;

public class Course {
    private int id;
    private  String name;
    private  String author;

    public Course(int id, String name, String author)
    {
        super(); //why this?
        this.author = author;
        this.name =name;
        this.id = id;


    }

    @Override
    public String toString() {
        return "Course{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", author='" + author + '\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }
}

CourseController

package com.mjfirstSBv5.sprintboot.learnspringboot;

//import org.springframework.web.bind.annotation.RestController;

import java.util.Arrays;
import java.util.List;

//@RestController
public class CourseController {

    public List<Course> retrieveAllCourses()
    {
        return Arrays.asList(
                new Course(1, "learn aws", "28min"),
                new Course(2, "learn spring boot", "28min" )

        );

    }

}

PS D：\AutoQA_Progress\intg-mock-service\learn-spring-boot\src\main\java\com\mjfirstSBv5\sprintboot\learnspringboot> javac Course.java
PS D：\AutoQA_Progress\intg-mock-service\learn-spring-boot\src\main\java\com\mjfirstSBv5\sprintboot\learnspringboot> javac CourseController.java
courseController.java：12：错误：无法找到符号public List retrieveAllCourses（）^
symbol：class课程
location：class
courseController.java：15：错误：找不到符号new Course（1，“learn aws”，“28 min”），^
symbol：class课程地点：类CourseController
courseController.java：16：错误：找不到符号新课程（2，“学习 Spring Boot ”，“28分钟”）^符号：课程地点：类CourseController
3错误PS D：\AutoQA_Progress\intg-mock-service\learn-spring-boot\src\main\java\com\mjfirstSBv5\sprintboot\learnspringboot>
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