java语言程序设计 10.9 改写Course类

package object10;import java.util.*;public class Course {private String courseName;private ArrayList<String>students=new ArrayList<String>();private int numOfStudents;public Course(String courseName){this.courseName=courseName;}public String getCourseName(){return courseName;}public void addStudents(String student){students.add(student);}public ArrayList<String> getStudents(){return students;}public int getNumberOfStudents(){return students.size();}public void dropStudents(String student){students.remove(student);}public void clear(){students.clear();}}