single linked list - java

[omcmb]

i am trying to write a program that implemets an interface using single linked list. i then am writing a tester program for the implementations. i am not sure if what i have done so far is correct, and some i have nothing for yet besides simple return statements. the ones that have just simple return statements are the ones i am unsure about, and the ones i have done, if they are not correct, please let me know. any help is appreciated.

import java.util.*;
import java.util.text;
public interface List {
//Appends the specified element to the end of this list and returns the specific position at which it was added.
public int add(Object o){
if (head == null){
head = new Node (o, null);
count++;
}
else

Node current = head;
while (current.link != null){
current = current.link;
}
current.link = new Node (o, null);
count++;
}

//Inserts the specified element at the specified position in this list.
public void add(int index, Object o){
if (head == null){
head = new Node (o, null);
count++;
}
else

Node current = head;
while (current.link != null){
current = current.link;
}
current.link = new Node (o, null);
count++;
}

}

//Removes all of the elements from this list.
public void clear(){
}



//Returns true if this list contains the specified element.
public boolean contains(Object element){
return false;
}

//Compares the specified object with this list for equality.
public boolean equals(Object element){
return false;
}

//Returns the element at the specified position in this list.
public Object get(int index){
return info;
}

//Returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.
public int indexOf(Object element){
}


//Returns true if this list contains no elements.
public boolean isEmpty(){
if (head == null)
return false;
}

//Removes the element at the specified position in this list.
public Object remove(int index){
if (move == n) {
move = n.getNext();
}
else {
Node tmp = move;
while (tmp.getNext() != n) tmp = tmp.getNext();
tmp.setNext( n.getNext() );
}



//Replaces the element at the specified position in this list with the specified element.
public Object set(int index, Object o){
return null;
}

//Returns the number of elements in this list.
public int size(){
return -1;
}

//Returns an array containing all of the elements in this list in proper sequence
public Object[] toArray(){
return null;
}

// Returns a String representation of the list.
public String toString()
{
String result = "";
NumListNode current = NumListNode;
while (current != null)
{
result += current.numbers + "\n";
current = current.next;
}
return result;

}

[jkrohn]

Use the CODE tag and indent that code.