Main.java Source code

Introduction

Here is the source code for Main.java

Source

public class Main {
    public static void main(String[] args) {
        LinkedList theList = new LinkedList();
        LinkedListIterator theItr;

        theItr = theList.zeroth();
        printList(theList);

        for (int i = 0; i < 10; i++) {
            theList.insert(new Integer(i), theItr);
            printList(theList);
            theItr.advance();
        }
        System.out.println("Size was: " + listSize(theList));

    }

    public static int listSize(LinkedList theList) {
        LinkedListIterator itr;
        int size = 0;
        for (itr = theList.first(); itr.isValid(); itr.advance())
            size++;
        return size;
    }

    public static void printList(LinkedList theList) {
        if (theList.isEmpty())
            System.out.print("Empty list");
        else {
            LinkedListIterator itr = theList.first();
            for (; itr.isValid(); itr.advance())
                System.out.print(itr.retrieve() + " ");
        }
        System.out.println();
    }
}

class LinkedList {
    public LinkedList() {
        header = new ListNode(null);
    }

    public boolean isEmpty() {
        return header.next == null;
    }

    public void makeEmpty() {
        header.next = null;
    }

    public LinkedListIterator zeroth() {
        return new LinkedListIterator(header);
    }

    public LinkedListIterator first() {
        return new LinkedListIterator(header.next);
    }

    public void insert(Object x, LinkedListIterator p) {
        if (p != null && p.current != null)
            p.current.next = new ListNode(x, p.current.next);
    }

    public LinkedListIterator find(Object x) {
        ListNode itr = header.next;

        while (itr != null && !itr.element.equals(x))
            itr = itr.next;

        return new LinkedListIterator(itr);
    }

    public LinkedListIterator findPrevious(Object x) {
        ListNode itr = header;

        while (itr.next != null && !itr.next.element.equals(x))
            itr = itr.next;

        return new LinkedListIterator(itr);
    }

    public void remove(Object x) {
        LinkedListIterator p = findPrevious(x);

        if (p.current.next != null)
            p.current.next = p.current.next.next; // Bypass deleted node
    }

    private ListNode header;

}

class LinkedListIterator {
    LinkedListIterator(ListNode theNode) {
        current = theNode;
    }

    public boolean isValid() {
        return current != null;
    }

    public Object retrieve() {
        return isValid() ? current.element : null;
    }

    public void advance() {
        if (isValid())
            current = current.next;
    }

    ListNode current;
}

class ListNode {
    public ListNode(Object theElement) {
        this(theElement, null);
    }

    public ListNode(Object theElement, ListNode n) {
        element = theElement;
        next = n;
    }

    public Object element;

    public ListNode next;
}