public abstract class SortedLinkedList {
 SortedLinkedListNode head;

 public abstract void insert(Comparable c);

 public String toString() {
    StringBuilder sb = new StringBuilder();
    SortedLinkedListNode currentNode = head.next;
    String comma = "";
    while (currentNode != null) {
      sb.append(comma);
      sb.append(currentNode.content);
      comma = ", ";
      currentNode = currentNode.next;
    }
    return sb.toString();
  }
}