How do I go about adding an object to an ArrayList?

Here's my main class:

import java.util.ArrayList;

public class Course {
  
   private String courseName;
   private ArrayList students = new ArrayList<>();
   private int numberOfStudents;
  
   public Course(String courseName) {
       this.courseName = courseName;
   }
  
   public void addStudent(ArrayList students) {
       this.students = students;
       students.add(students);
       numberOfStudents ++;
   }
  
   public ArrayList getStudents() {
       return students;
   }
  
   public int getNumberOfStudents() {
       return numberOfStudents;
   }
  
   public String getCourseName() {
       return courseName;
   }
  
   public void dropStudents(ArrayList students) {
       this.students = students;
       students.remove(students);
       numberOfStudents --;
   }
}

Here is my test class:

public class TestCourse {

   public static void main(String[] args) {
       Course course1 = new Course("Data Structures");
       Course course2 = new Course("Database Systems");
      
       course1.addStudent("Peter Jones");
   }
}

I get that I can't add a string to an ArrayList, but how do I add an object to it?