Circular Classes / Cycling Star - Graph

[Kepler Nasa]

Hey all,

is there any way of implementing cyclic / circular classes in Java or Scala?

For Example:

public class Person {
	private String name;
	private int age;
	private Set<Group> groups;
	
	public Person() {
	}
	
	public setName(String name) {
		this.name = name;
	} 
	
	public setAge(int age) {
		this.age = age;
	}
	
	public setGroups(ArrayList<Group> groups) {
		this.groups = groups;
	}
}

public class Group {
	private List<Person> persons = new ArrayList<>();
	
	public Group() {
	}
	
	public setPersons(List<Person> persons){
		this.persons = persons;
	}
	
}

public class groupEmUp{
	Person p1 = new Person();
	p1.setAge(20);
	p1.setName("Test1");
	Person p2 = new Person();
	p2.setAge(20);
	p2.setName("Test2");
	
	Group friends = new Group();
	
	// cycling references
	
}

As you can see a Person has Set of Groups, and Groups can have List of Persons, whereas Persons have Groups again.
Person <- Group(s) <- Person <- Group(s) <- ...

How can I put a reference to it in Groups?

[Les Morgan]

Shouldn't be a problem in Java:

public class Junk{
  public static void main(String[] args) {
    A a = new A();
    a.b = new B();
    a.b.a = a;
    a.b.p();
    a.b.a.p();
    a.b.a.b.p();
    a.b.a.b.a.p();
  }
}
class A{
  public B b;
  public void p(){
    System.out.println("This is A");
  }
}
class B{
  public A a;
  public void p(){
    System.out.println("This is B");
  }  
}

Java does not do any encapsulation of the object, you are just working with references.