使用java生成设计一个教材类，一个课程类，及一个为某门课程指定参考教材的类。一门课程可以有多本参考教材，再设计一个测试类。

教材类：

public class Textbook {
    private String title;
    private String author;
    private String publisher;
    private int year;

    public Textbook(String title, String author, String publisher, int year) {
        this.title = title;
        this.author = author;
        this.publisher = publisher;
        this.year = year;
    }

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }

    public String getPublisher() {
        return publisher;
    }

    public int getYear() {
        return year;
    }
}

课程类：

import java.util.ArrayList;

public class Course {
    private String name;
    private ArrayList<Textbook> textbooks;

    public Course(String name) {
        this.name = name;
        this.textbooks = new ArrayList<>();
    }

    public String getName() {
        return name;
    }

    public void addTextbook(Textbook textbook) {
        textbooks.add(textbook);
    }

    public ArrayList<Textbook> getTextbooks() {
        return textbooks;
    }
}

为某门课程指定参考教材的类：

public class CourseTextbook {
    private Course course;
    private Textbook textbook;

    public CourseTextbook(Course course, Textbook textbook) {
        this.course = course;
        this.textbook = textbook;
        course.addTextbook(textbook);
    }

    public Course getCourse() {
        return course;
    }

    public Textbook getTextbook() {
        return textbook;
    }
}

测试类：

public class Test {
    public static void main(String[] args) {
        Course course = new Course("Java Programming");
        Textbook textbook1 = new Textbook("Java: A Beginner's Guide", "Herbert Schildt", "McGraw-Hill", 2018);
        Textbook textbook2 = new Textbook("Head First Java", "Kathy Sierra and Bert Bates", "O'Reilly Media", 2005);
        CourseTextbook courseTextbook1 = new CourseTextbook(course, textbook1);
        CourseTextbook courseTextbook2 = new CourseTextbook(course, textbook2);

        System.out.println("Course: " + course.getName());
        System.out.println("Textbooks:");
        for (Textbook textbook : course.getTextbooks()) {
            System.out.println(textbook.getTitle() + ", " + textbook.getAuthor() + ", " +
                    textbook.getPublisher() + ", " + textbook.getYear());
        }
    }
}

输出：

Course: Java Programming
Textbooks:
Java: A Beginner's Guide, Herbert Schildt, McGraw-Hill, 2018
Head First Java, Kathy Sierra and Bert Bates, O'Reilly Media, 2005