Cannot Find Symbol

[soeca]

Ciao ragazzi ho da poco intrapreso lo studio degli iteratori e delle PositionList in JAVA! Sto avendo però alcuni problemi per quanto riguarda la compilazione delle seguenti interfacce:
Position.java

interface Position <E> 
{
	E element();
}

PositionList.java

 interface PositionList <E>
{
	public int size();
	public Position <E> first();
	public Position <E> last();
	public Position <E> prev(Position<E> p);
	public Position <E> next(Position<E> n);
	public boolean isEmpty();
	public void addFirst(E element);
	public void addLast(E element);
	public void addBefore(Position <E> p, E element);
	public void addAfter(Position <E> p, E element);
	public E remove(Position <E> p);
	public E set(Position <E> p, E element);
}

Queste due interfacce si trovano nello stesso package però la prima se provo a compilarla da terminale ottengo esito positivo; la seconda invece ottengo i seguenti errori:

javac /media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti\ Java/PositionListGeneric/src/PositionList.java
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:4: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public Position <E> first();
	       ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:5: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public Position <E> last();
	       ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:6: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public Position <E> prev(Position<E> p);
	                         ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:6: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public Position <E> prev(Position<E> p);
	       ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:7: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public Position <E> next(Position<E> n);
	                         ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:7: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public Position <E> next(Position<E> n);
	       ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:11: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public void addBefore(Position <E> p, E element);
	                      ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:12: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public void addAfter(Position <E> p, E element);
	                     ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:13: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public E remove(Position <E> p);
	                ^
/media/9d893d0a-fa19-414d-9467-39bebc3e9454/Progetti Java/PositionListGeneric/src/PositionList.java:14: cannot find symbol
symbol  : class Position
location: interface PositionList<E>
	public E set(Position <E> p, E element);
	             ^
10 errors

la domanda è perchè non ne vuole sapere di compilare?? Grazie a tutti.