University project - Library Program.

Hello everyone.
I am kinda a beginner, been java programming for 3-4 months, but i learn fast.
I have a java programming project, a gui library system, something complex.
User has to create library, then add books, delete books, add chapters in book, remove chapter.

First i have to do 6 classes( architecture, they name it):
- class Library: contains objects of type Book and implements ILibrary
- class Book: contains objects of type Chapter and book name and implements IBook
- class Chapter: contains objects of type Paragraph and chapter name si and implements IChapter
- class Sentence: extends ArrayList<String> and retain one sentence
- class Paragraph: extends Body<Sentence> and retain one or more sentences, so a paragraph
- class Body: implements Collection and can retain only objects of the same type in a ArrayList

I did 3 classes for this 6. But i stuck at class Body, i did not learn about parameterized class, so i don't know how to declare it. Can someone help me with Body class and Paragraph class?

Especially i stuck at build constructors. I don't know what to do with the <E> from Body

Code :

---

package element;
 
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
 
public class Body<E> implements Collection {
 
    private E item;
    private ArrayList<E> items = new ArrayList<E>();
 
    @Override
    public int size() {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean isEmpty() {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean contains(Object o) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public Iterator iterator() {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public Object[] toArray() {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public Object[] toArray(Object[] a) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean add(Object e) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean remove(Object o) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean containsAll(Collection c) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean addAll(Collection c) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean removeAll(Collection c) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public boolean retainAll(Collection c) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
    @Override
    public void clear() {
        throw new UnsupportedOperationException("Not supported yet.");
    }
 
}

---

I'm a still a student and a beginner in java, so please bear with me. :)

Ignore javadoc becouse is in romanian(my language

Nobody can help me with this class? I can't find a convincing example with parameterized class.