Entity class implementation and abstract data type implementation

Question

What is an entity class and how do I implement it? I am required to write a member management program using adt implementation. So I assume my entity class would be the member management. Is it something likepublic class member extends LinkedList? Note: I am not allowed to use java.util.list etc

Currently I have a

1. java interface public interface ListInterface<T>
2. java class public class LinkedList<T> implements ListInterface<T>

public interface ListInterface<T> {
    public boolean add(T newEntry);
    public boolean add(int newPosition, T newEntry);
    public T remove(int givenPosition);
    public void clear();    
    public boolean replace(int givenPosition, T newEntry);
    public boolean contains(T anEntry);
    public int getNumberOfEntries();
    public boolean isEmpty();
    public boolean isFull();
}