public class LinkedIntListSolution {
    private ListNode front;
    private int size;
    
    public void moveSecondLastToFront() {
        if (this.front != null &&
            this.front.next != null &&
            this.front.next.next != null) {
            ListNode thirdToLast = this.front;
            while (thirdToLast.next.next.next != null) {
                thirdToLast = thirdToLast.next;
            }

            ListNode secondToLast = thirdToLast.next;
            thirdToLast.next = secondToLast.next;
            secondToLast.next = this.front;
            this.front = secondToLast;
        }
    }
    
    /** Creates a new empty LinkedIntList */
    public LinkedIntListSolution() {
        this.front = null;
    }
    
    /** Constructs a String representation of the LinkedIntList.
     *  For example, "[1, 2, 3]".
     */
    public String toString() {
        String result = "[";
        ListNode current = this.front;
        
        // Process all but the last element of the LinkedList
        while (current != null && current.next != null) {
            result += current.data + ", ";
            current = current.next;
        }
        
        // Process the last element (if one exists)
        if (current != null) {
            result += current.data;
        }
        
        return result + "]";
    }
    
    /** Appends value to the end of the LinkedIntList. */
    public void add(int value) {
        if (this.front == null) {
            this.front = new ListNode(value);
        }
        else {
            ListNode current = this.front;
            while (current.next != null) {
                current = current.next;
            }
            current.next = new ListNode(value);
        }
        this.size++;
    }
    
    /** Returns the size of the LinkedIntList */
    public int size() {
        return this.size;
    }
    
    /** Returns the data at index.
     *  pre: 0 <= index <= size, otherwise throws IllegalArgumentException
     */
      public int get(int index) {
        checkIndex(index);

        ListNode current = this.front;
        for (int i = 0; i < index; i++) {
            current = current.next;
        }
        return current.data;
    }
    
    /** Sets the data at index to value. 
     *  pre: 0 <= index <= size, otherwise throws IllegalArgumentException
     */
    public void set(int index, int value) {
        checkIndex(index);

        ListNode current = this.front;
        for (int i = 0; i < index; i++) {
            current = current.next;
        }
        
        current.data = value;       
    }
    
    /** Checks that index is within valid bounds
     *  for the LinkedIntList.
     *  pre: 0 <= index <= size, otherwise throws IllegalArgumentException
     */
    private void checkIndex(int index) {
        if (index < 0 || index >= this.size) {
            throw new IllegalArgumentException();
        }
    }
    
    /**
     * ListNode is a class for storing a single node of a linked list that stores
     * int values. It stores an integer value and a link to the next node of the
     * linked list.
     * 
     * @author Adam Blank
     */

    private class ListNode {
        public int data;
        public ListNode next;

        /** Creates a terminal ListNode with 0 as its data. */
        public ListNode() {
            this(0, null);
        }

        /** Creates a terminal ListNode with data as its data. */
        public ListNode(int data) {
            this(data, null);
        }

        /** Creates a ListNode with data as its data that points to next */
        public ListNode(int data, ListNode next) {
            this.data = data;
            this.next = next;
        }
    }
}