In a Java class method, how can I iterate through an arraylist and return every object so that it can be added to a new arraylist in a different class?

For example:

public class Course { 

private ArrayList courseStudents = new ArrayList<>(); // Students in a course that professor is teaching 

//code to add student to courseStudents would be here public Student getStudent(){ if(!courseStudents.isEmpty()){ for(Student i : courseStudents){ return i; } } System.out.println("This instructor is not teaching any students."); return null; }}

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public class Student { private String name; // the student's name private String id; // the student's id number

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public class Instructor { private String name; private ArrayList profStudents = new ArrayList<>(); // Students the prof is teaching private ArrayList profCourses = new ArrayList<>(); // courses the prof is teaching 

//when a professor is assigned to a course to teach, I want all student objects to be added to the profStudents arraylist //this is the last line of code I have in this assigncourse method but it does not properly add a student object to the profStudents arraylist profStudents.add(course.getStudent());