Hello I was wondering If someone can help me understand this concept in Java. Can you finish the example?

EXAMPLE:

Public class Zoo$\{$

$//$Zoo class members $($instance vars, constructors, setter$/$getters$,$ etc.$)$

String zooName;

Int area;

Int noOfAnimals;

$\}$

Public class Animals$\{$

Zoo animals $=$ new Zoo$()$; $//$instance var of Zoo

$//$ Animal class members $($instance vars, constructors, setters$/$getters$,$ etc.$)$

String animalType;

String color;

Int ID;

Boolean isAFemale;

$\}$

All I really know is that Animal class $($second class$)$ is supposed to have field type from class Zoo$($First defined class$)$ and neither class should have main in them.

Thanks