Learning ADT lists

how do I implement these 3 methods contains(), remove() and clear().

 public boolean contains(T item);
   // Determines if a certain item is in the list.
   // Precondition: an item which need to be compared
   // Postcondition: Returns true if there is the same item in the list
   // Return false if there is not the same item in the list

  public boolean remove(int position);
   // Deletes an item from the list at a given position.
   // Precondition: position indicates where the deletion should occur.
   // Postcondition: If 1 <= index <= size(), the item at a given position
   // in the list is deleted, other items are renumbered
accordingly
   // and, it returns true.
   // Returns false if index < 1 or index > size()+1
   // or the list is empty

  public void clear();
   // Deletes all the items from the list.
   // Precondition: None.
   // Postcondition: The list is empty.

} // end ListInterface

public class ADTList<T> implements ListInterface<T>{

    private T array[];
    private int numItems;

    public ADTList(){

        //create an empty array
        array = (T[]) new Object[10];
        // assign 0 to numItems;
        numItems=0;
    }

    }

   public boolean contains(T item){
        System.out.println("You need to implement it");
        return true;
    }

   public boolean remove(int position){
        System.out.println("You need to implement it");
        return true;
    }

   public void clear(){
        System.out.println("You need to implement it");
    }

}

if someone could show me how to do one of these 3 methods I think I can
figure out the other two. Thanks in advance for any help offered.