Simple error handling

Question

how can i catch a NullPointerException and print the line "The list is empty" across an entire class, without modifying every individual method?

Answer 1

The problem is that when i try to call any mutator method on the list, when there is infact no list, the class will throw a NullPointerException
What i want is that System.err.println("The List is empty"); is called whenever a NullPointerException occurs, rather than just crashing the program...
i could always do try, catch in every single method... but i thought there must be a cleaner way of doing this...
here's the code:
public class StringLinkedList
    private ListNode head;
    public StringLinkedList()
        head = null;
    public String getLast() {
        ListNode position = head;
        while (position.getLink() != null)
            position = position.getLink();
        return position.getData();
    public String getBeforeLast() {
        ListNode position = head;
        while ((position.getLink()).getLink() != null)
            position = position.getLink();
        return position.getData();
    public int length()
        int count = 0;
        ListNode position = head;
        while (position != null)
            count++;
            position = position.getLink();
        return count;
    public void addANodeToStart(String addData)
        head = new ListNode(addData, head);
    public void addANodeToEnd(String addData) {
        ListNode tail = new ListNode(addData, null);
        ListNode position = head;
        while (position.getLink()!= null) {
            position = position.getLink();
        position.setLink(tail);
    public void deleteHeadNode()
        if (head != null)
            head = head.getLink();
        else
            System.out.println("Deleting from an empty list.");
            System.exit(0);
    public boolean onList(String target)
        return (Find(target) != null);
    private ListNode Find(String target)
        ListNode position;
        position = head;
        String dataAtPosition;
        while (position != null)
            dataAtPosition = position.getData();
            if (dataAtPosition.equals(target))
                return position;
            position = position.getLink();
        return null;
    public void showList()
        ListNode position;
        position = head;
        while (position != null)
            System.out.println(position.getData());
            position = position.getLink();
}the second class...
public class ListNode
    private String data;
    private ListNode link;
    public ListNode()
        link = null;
        data = null;
    public ListNode(String newData, ListNode linkValue)
        data = newData;
        link = linkValue;
    public void setData(String newData)
        data = newData;
    public String getData()
        return data;
    public void setLink(ListNode newLink)
        link = newLink;
    public ListNode getLink()
        return link;
}