用Java代码编写一个在线学习系统程序，实现课程加入、撤销、课程信息修改、课程信息查询等功能

好的，我可以给您提供一个简单的Java代码示例来实现在线学习系统程序。以下是代码实现：

import java.util.ArrayList;
import java.util.List;

// 课程类
class Course {
    private String courseId;  // 课程编号
    private String courseName;  // 课程名称
    private String courseIntro;  // 课程介绍
    private int selectedNum;  // 已选人数

    public Course(String courseId, String courseName, String courseIntro) {
        this.courseId = courseId;
        this.courseName = courseName;
        this.courseIntro = courseIntro;
        this.selectedNum = 0;
    }

    public String getCourseId() {
        return courseId;
    }

    public void setCourseId(String courseId) {
        this.courseId = courseId;
    }

    public String getCourseName() {
        return courseName;
    }

    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }

    public String getCourseIntro() {
        return courseIntro;
    }

    public void setCourseIntro(String courseIntro) {
        this.courseIntro = courseIntro;
    }

    public int getSelectedNum() {
        return selectedNum;
    }

    public void setSelectedNum(int selectedNum) {
        this.selectedNum = selectedNum;
    }

    @Override
    public String toString() {
        return "Course{" +
                "courseId='" + courseId + '\'' +
                ", courseName='" + courseName + '\'' +
                ", courseIntro='" + courseIntro + '\'' +
                ", selectedNum=" + selectedNum +
                '}';
    }
}

// 学生类
class Student {
    private String studentId;  // 学生编号
    private String studentName;  // 学生姓名
    private List<Course> selectedCourses;  // 已选课程列表

    public Student(String studentId, String studentName) {
        this.studentId = studentId;
        this.studentName = studentName;
        this.selectedCourses = new ArrayList<>();
    }

    public String getStudentId() {
        return studentId;
    }

    public void setStudentId(String studentId) {
        this.studentId = studentId;
    }

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    public List<Course> getSelectedCourses() {
        return selectedCourses;
    }

    public void setSelectedCourses(List<Course> selectedCourses) {
        this.selectedCourses = selectedCourses;
    }

    @Override
    public String toString() {
        return "Student{" +
                "studentId='" + studentId + '\'' +
                ", studentName='" + studentName + '\'' +
                ", selectedCourses=" + selectedCourses +
                '}';
    }
}

// 在线学习系统类
class OnlineLearningSystem {
    private List<Course> courseList;  // 课程列表
    private List<Student> studentList;  // 学生列表

    public OnlineLearningSystem() {
        this.courseList = new ArrayList<>();
        this.studentList = new ArrayList<>();
    }

    // 课程加入
    public void addCourse(Course course) {
        courseList.add(course);
        System.out.println("课程 " + course.getCourseName() + " 添加成功！");
    }

    // 课程撤销
    public void removeCourse(String courseId) {
        Course targetCourse = null;
        for (Course course : courseList) {
            if (course.getCourseId().equals(courseId)) {
                targetCourse = course;
                break;
            }
        }
        if (targetCourse != null) {
            courseList.remove(targetCourse);
            System.out.println("课程 " + targetCourse.getCourseName() + " 撤销成功！");
        } else {
            System.out.println("未找到编号为 " + courseId + " 的课程！");
        }
    }

    // 课程信息修改
    public void modifyCourse(String courseId, String courseName, String courseIntro) {
        Course targetCourse = null;
        for (Course course : courseList) {
            if (course.getCourseId().equals(courseId)) {
                targetCourse = course;
                break;
            }
        }
        if (targetCourse != null) {
            targetCourse.setCourseName(courseName);
            targetCourse.setCourseIntro(courseIntro);
            System.out.println("课程 " + targetCourse.getCourseName() + " 修改成功！");
        } else {
            System.out.println("未找到编号为 " + courseId + " 的课程！");
        }
    }

    // 课程信息查询
    public void queryCourse(String keyword) {
        List<Course> result = new ArrayList<>();
        for (Course course : courseList) {
            if (course.getCourseId().contains(keyword) || course.getCourseName().contains(keyword)) {
                result.add(course);
            }
        }
        if (result.size() > 0) {
            System.out.println("查询结果如下：");
            for (Course course : result) {
                System.out.println(course);
            }
        } else {
            System.out.println("未找到相关课程！");
        }
    }

    // 学生选课
    public void chooseCourse(String studentId, String courseId) {
        Course targetCourse = null;
        for (Course course : courseList) {
            if (course.getCourseId().equals(courseId)) {
                targetCourse = course;
                break;
            }
        }
        if (targetCourse != null) {
            if (targetCourse.getSelectedNum() >= 10) {
                System.out.println("课程 " + targetCourse.getCourseName() + " 选课人数已满！");
            } else {
                Student targetStudent = null;
                for (Student student : studentList) {
                    if (student.getStudentId().equals(studentId)) {
                        targetStudent = student;
                        break;
                    }
                }
                if (targetStudent != null) {
                    if (targetStudent.getSelectedCourses().contains(targetCourse)) {
                        System.out.println("学生 " + targetStudent.getStudentName() + " 已选过该课程！");
                    } else {
                        targetStudent.getSelectedCourses().add(targetCourse);
                        targetCourse.setSelectedNum(targetCourse.getSelectedNum() + 1);
                        System.out.println("学生 " + targetStudent.getStudentName() + " 选课成功！");
                    }
                } else {
                    System.out.println("未找到编号为 " + studentId + " 的学生！");
                }
            }
        } else {
            System.out.println("未找到编号为 " + courseId + " 的课程！");
        }
    }

    // 学生退课
    public void dropCourse(String studentId, String courseId) {
        Course targetCourse = null;
        for (Course course : courseList) {
            if (course.getCourseId().equals(courseId)) {
                targetCourse = course;
                break;
            }
        }
        if (targetCourse != null) {
            Student targetStudent = null;
            for (Student student : studentList) {
                if (student.getStudentId().equals(studentId)) {
                    targetStudent = student;
                    break;
                }
            }
            if (targetStudent != null) {
                if (targetStudent.getSelectedCourses().contains(targetCourse)) {
                    targetStudent.getSelectedCourses().remove(targetCourse);
                    targetCourse.setSelectedNum(targetCourse.getSelectedNum() - 1);
                    System.out.println("学生 " + targetStudent.getStudentName() + " 退课成功！");
                } else {
                    System.out.println("学生 " + targetStudent.getStudentName() + " 未选过该课程！");
                }
            } else {
                System.out.println("未找到编号为 " + studentId + " 的学生！");
            }
        } else {
            System.out.println("未找到编号为 " + courseId + " 的课程！");
        }
    }

    // 学生已选课程查询
    public void querySelectedCourse(String studentId) {
        Student targetStudent = null;
        for (Student student : studentList) {
            if (student.getStudentId().equals(studentId)) {
                targetStudent = student;
                break;
            }
        }
        if (targetStudent != null) {
            if (targetStudent.getSelectedCourses().size() > 0) {
                System.out.println("学生 " + targetStudent.getStudentName() + " 已选课程如下：");
                for (Course course : targetStudent.getSelectedCourses()) {
                    System.out.println(course);
                }
            } else {
                System.out.println("学生 " + targetStudent.getStudentName() + " 未选任何课程！");
            }
        } else {
            System.out.println("未找到编号为 " + studentId + " 的学生！");
        }
    }
}

// 测试类
public class Test {
    public static void main(String[] args) {
        OnlineLearningSystem system = new OnlineLearningSystem();

        // 添加课程
        system.addCourse(new Course("C001", "Java程序设计", "Java基础知识和程序设计"));
        system.addCourse(new Course("C002", "Web开发技术", "Web开发中的HTML、CSS、JavaScript等技术"));
        system.addCourse(new Course("C003", "数据库设计", "数据库基础知识和设计技术"));

        // 查询课程
        system.queryCourse("Java");

        // 修改课程信息
        system.modifyCourse("C001", "Java程序设计（进阶）", "Java高级知识和程序设计");

        // 学生选课
        system.chooseCourse("S001", "C001");
        system.chooseCourse("S001", "C002");
        system.chooseCourse("S002", "C001");
        system.chooseCourse("S003", "C001");
        system.chooseCourse("S004", "C001");
        system.chooseCourse("S005", "C001");
        system.chooseCourse("S006", "C001");
        system.chooseCourse("S007", "C001");
        system.chooseCourse("S008", "C001");
        system.chooseCourse("S009", "C001");
        system.chooseCourse("S010", "C001");
        system.chooseCourse("S011", "C001");

        // 学生已选课程查询
        system.querySelectedCourse("S001");

        // 学生退课
        system.dropCourse("S001", "C002");

        // 课程撤销
        system.removeCourse("C003");
    }
}

以上代码实现了课程加入、撤销、课程信息修改、课程信息查询、学生选课、学生退课、学生已选课程查询等功能，您可以根据需要进行修改或完善。同时，需要注意的是，以上代码只是一个简单的实现示例，实际应用中需要考虑到更多的细节问题。