"Write a program to display a linked list graphically. Draw each element of the list as a box, and indicate the links with line segments. Draw an iterator as in Figure 15-3. Supply buttons to move the iterator and to add and remove elements."
The elements of the node appear as boxes, with a number in them, connected by lines. Much of teh following code was given to me, the parts I have written are the draw methods, as indicated by the question. So far when i run the program, the buttons show up, but not of them do anything. This is a lot of code, but I appreciate any help given.
package Question2;
import javax.swing.JFrame;
/**
Displays a linked list.
*/
public class LinkedListViewer
{
public static void main(String args[])
{
JFrame frame = new LinkedListFrame();
frame.setTitle("LinkedListViewer");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}package Question2;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class LinkedListFrame extends JFrame
{
public LinkedListFrame()
{
setSize(FRAME_WIDTH, FRAME_HEIGHT);
JPanel panel = new JPanel();
panel.add(makeButtonPanel ());
component = new LinkedListComponent();
component.setPreferredSize(new Dimension(
COMPONENT_WIDTH, COMPONENT_HEIGHT));
panel.add(component);
add(panel);
}
private JPanel makeButtonPanel()
{
JPanel panel = new JPanel();
addButton = new JButton("Add");
addButton.addActionListener(new AddButtonListener());
panel.add(addButton);
newButton = new JButton("New Iter");
newButton.addActionListener(new NewButtonListener());
panel.add(newButton);
nextButton = new JButton("Next");
nextButton.addActionListener(new NextButtonListener());
panel.add(nextButton);
removeButton = new JButton("Remove");
removeButton.addActionListener(new RemoveButtonListener());
panel.add(removeButton);
return panel;
}
class AddButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
component.add();
}
}
class NewButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
component.newIterator();
}
}
class NextButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
component.next();
}
}
class RemoveButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
component. remove();
}
}
private JButton newButton;
private JButton nextButton;
private JButton addButton;
private JButton removeButton;
private LinkedListComponent component;
private static final int FRAME_WIDTH = 500;
private static final int FRAME_HEIGHT = 400;
private static final int COMPONENT_WIDTH = 500;
private static final int COMPONENT_HEIGHT = 350;
}package Question2;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JComponent;
public class LinkedListComponent extends JComponent
{
public LinkedListComponent()
{
list = new LinkedList();
newIterator();
next = 1;
}
public void newIterator()
{
iterator = (LinkedListIterator) list.listIterator();
repaint();
removeOk = false;
}
public void next()
{
if (iterator.hasNext())
{
iterator.next();
repaint();
removeOk = true;
}
}
public void add()
{
iterator.add(new Integer(next));
next++;
repaint();
removeOk = false;
}
public void remove()
{
if (removeOk)
{
iterator.remove();
repaint();
removeOk = false;
}
}
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
list.draw(g2);
if (iterator != null)
iterator.draw(g2);
}
private LinkedList list;
private LinkedListIterator iterator;
private int next = 1;
private boolean removeOk = false;
}package Question2;
import java.awt.Graphics2D;
import java.util.NoSuchElementException;
public class LinkedListIterator implements ListIterator
{
/**
Constructs an iterator that points to the front
of the linked list.
*/
public LinkedListIterator()
{
position = null;
previous = null;
}
private class Node
{
public Object data;
public Node next;
}
/**
Adds an element to the front of the linked list.
@param element the element to add
*/
public void addfirst(Object element)
{
Node newNode = new Node();
newNode.data = element;
newNode.next = first;
first = newNode;
}
/**
Moves the iterator past the next element.
@return the traversed element
*/
public Object next()
{
if (!hasNext())
throw new NoSuchElementException();
previous = position; // Remember for remove
if (position == null)
position = first;
else
position = position. next;
return position.data;
}
/**
Tests if there is an element after the iterator
position.
@return true if there is an element after the iterator
position
*/
public boolean hasNext()
{
if (position == null)
return first != null;
else
return position.next != null;
}
/**
Adds an element before the iterator position
and moves the iterator past the inserted element.
@param element the element to add
*/
public void add(Object element)
{
if (position == null)
{
addfirst(element);
position = first;
}
else
{
Node newNode = new Node();
newNode.data = element;
newNode.next = position.next;
position.next = newNode;
position = newNode;
}
previous = position;
}
/**
Removes the first element in the linked list.
@return the removed element
*/
public Object removefirst()
{
if (first == null)
throw new NoSuchElementException();
Object element = first.data;
first = first.next;
return element;
}
/**
Removes the last traversed element. This method may
only be called after a call to the next() method.
*/
public void remove()
{
if (previous == position)
throw new IllegalStateException();
if (position == first)
{
removefirst();
}
else
{
previous.next = position.next;
}
position = previous;
}
/**
Sets the last traversed element to a different
value.
@param element the element to set
*/
public void set(Object element)
{
if (position == null)
throw new NoSuchElementException();
position. data = element;
}
public void draw(Graphics2D g2)
{
// TODO: Draw iterator
LinkedList.draw(g2);
}
private Node position;
private Node previous;
private Node first;
}package Question2;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.Line2D;
import java.util.NoSuchElementException;
/**
A linked list is a sequence of nodes with efficient
element insertion and removal. This class
contains a subset of the methods of the standard
java.util.LinkedList class.
*/
public class LinkedList
{
/**
Constructs an empty linked list.
*/
public LinkedList()
{
first = null;
}
/**
Returns the first element in the linked list.
@return the first element in the linked list
*/
public Object getFirst()
{
if (first == null)
throw new NoSuchElementException();
return first.data;
}
/**
Removes the first element in the linked list.
@return the removed element
*/
public Object removeFirst()
{
if (first == null)
throw new NoSuchElementException();
Object element = first.data;
first = first.next;
return element;
}
/**
Adds an element to the front of the linked list.
@param element the element to add
*/
public void addfirst(Object element)
{
Node newNode = new Node();
newNode.data = element;
newNode.next = first;
first = newNode;
}
/**
Returns an iterator for iterating through this list.
@return an iterator for iterating through this list
*/
public ListIterator listIterator()
{
return new LinkedListIterator();
}
public static void draw(Graphics2D g2)
{
// TODO: Draw all nodes
for (int i = 0; i < count; i++)
{
Rectangle node = new Rectangle((int)(points.get(i).getX()), (int)(points.get(i).getY()), 30, 30);
g2.draw(node);
}
}
public static int count = 0;
public static ArrayList<Point2D.Double> points;
private Node first;
private class Node
{
public Node()
{
// TODO: Determine coordinates for this node
if (LinkedList.count == 0)
{
LinkedList.points.add(new Point2D.Double(20, 20));
LinkedList.count++;
}
else
{
LinkedList.points.add(new Point2D.Double(30 + points.get(LinkedList.count).getX(), 30 + points.get(LinkedList.count).getY()));
LinkedList.count++;
}
}
public Object data;
public Node next;
// TODO: Instance fields for coordinates(Done)
}
}package Question2;
/**
A list iterator allows access of a position in a linked list.
This interface contains a subset of the methods of the
standard java.util.ListIterator interface. The methods for
backward traversal are not included.
*/
public interface ListIterator
{
/**
Moves the iterator past the next element.
@return the traversed element
*/
Object next();
/**
Tests if there is an element after the iterator
position.
@return true if there is an element after the iterator
position
*/
boolean hasNext();
/**
Adds an element before the iterator position
and moves the iterator past the inserted element.
@param element the element to add
*/
void add(Object element);
/**
Removes the last traversed element. This method may
only be called after a call to the next() method.
*/
void remove();
/**
Sets the last traversed element to a different
value.
@param element the element to set
*/
void set(Object element);
}
