Coloring a Dynamic Shape

Question

Hello, im stumped. I cant seem to figure out how i can color a randomly generated path.
The area in between the two lines is what i am trying to color. The path is randomly generated via two lines. I have access to every point in each line via x1Pos and x2Pos in gui.java.
How would you go about doing this? ( If [IMG] tags arent allowed then the following code has been tested and compiles with the standard library.)
Myframe.Java
import java.util.Random;
import javax.swing.JFrame;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
class MyFrame extends JFrame {
      static Gui gui;
      static Dimension frameSize;
      static boolean initialSet = false;
     public MyFrame()
          frameSize = new Dimension();
          Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
          frameSize.height = 500;
          frameSize.width = 500;
          setSize(frameSize);
          //center the frame
          setLocation((screenSize.width - frameSize.width)/2, (screenSize.height - frameSize.height)/2);
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          setTitle("Hello");
          setResizable(false);
          System.out.println("hello");
          Container contentPane = getContentPane();
          contentPane.setBackground(Color.white);
          gui = new Gui(frameSize.height/2);
          gui.setSize(frameSize);
          contentPane.add(gui);          
     public static class GuiLogic implements Runnable
          Thread t;
          Random rand;
          public  GuiLogic()
               t = new Thread(this, "Demo Thread");               
               rand = new Random();
               t.start();
          public int getX(int d, int x1)
               int x = x1 + d;               
               return x;
          public void run()
               int firstLine[] = new int[frameSize.height/2];
               int secondLine[] = new int[frameSize.height/2];
               int yPoint[] = new int[frameSize.height/2];
               int x1 = 0;
               int x2 = 0;
               int curveLength = 0;
               int pointsAdded = 0;
               int curveDirection = 0;          // 1 - left, 2 - right, 3 - straight
               boolean curveAdded = false;
               boolean curveStarted = false;               
               while(true)
                    //where the road should start (Higher value = lower positon)
                    int lastY = frameSize.height;
                    int width = 150;
                    int start = 150;
                    //set up initial coordinates
                    if(!initialSet)
                         //makes the first screen a straight path
                         for(int i = 0; i < frameSize.height/2; i++)
                              int y = lastY - 2;
                              lastY = y;
                              yPoint[i] = y;
                              firstLine[i] = start;
                              secondLine[i] = start + width;
                              gui.setCord(i, firstLine, yPoint[i], secondLine[i]);
                         initialSet = true;
                    //Generate all other coordinates
                    if(!curveStarted)
                         curveLength = rand.nextInt(100) + 30;
                         curveDirection = rand.nextInt(2) + 1;
                         curveAdded = false;
                    //if the current curveLength will make the path go within 30 pixels of the right edge
                    // and curve direction is right
                    //generate new direction and curve length
                    if(((firstLine[frameSize.height/2 - 1] + curveLength + width) >= (frameSize.width - 40)) && curveDirection == 2)
                         System.out.println("Right bound");
                         boolean direction;
                         curveLength = rand.nextInt(100) + 30;
                         direction = rand.nextBoolean();
                         if(direction)
                              curveDirection = 1;
                         } else
                              curveDirection = 3;
                    } else
                    //if the current curveLength will make the path go within 30 pixels of the left edge
                    //and curve direction is left
                    //generate new direction and curve length
                    if((firstLine[frameSize.height/2 - 1] - curveLength) <= 30 && curveDirection == 1)
                         System.out.println("left bound");
                         boolean direction;
                         curveLength = rand.nextInt(100) + 30;
                         direction = rand.nextBoolean();
                         if(direction)
                              curveDirection = 2;
                         } else
                              curveDirection = 3;
                    if(!curveAdded)
                         curveStarted = true;
                         //Right curve
                         if(curveDirection == 2)
                              x1 = firstLine[frameSize.height/2 - 1] + 1;
                              x2 = getX(width, x1);
                              pointsAdded++;
                         //left curve     
                         } else if(curveDirection == 1)
                              x1 = firstLine[frameSize.height/2 - 1] - 1;
                              x2 = getX(width, x1);
                              pointsAdded++;
                         //Straight
                         else if(curveDirection == 3)
                              x1 = firstLine[frameSize.height/2 - 1];
                              x2 = getX(width, x1);
                              pointsAdded++;
                         //check if done with last curve
                         if(pointsAdded >= curveLength)
                              pointsAdded = 0;
                              curveAdded = true;
                              curveStarted = false;                              
                    //Update Gui
                    //Buffer last points          
                    int buffer[] = new int[2];
                    buffer[0] = firstLine[frameSize.height/2 - 1];
                    buffer[1] = secondLine[frameSize.height/2 - 1];
                    //move all coordinates down
                    for(int i = 0; i < frameSize.height/2 - 2; i++)
                         firstLine[i] = firstLine[i + 1];
                         secondLine[i] = secondLine[i + 1];                         
                    //add the buffered coordinate and the new coordinate
                         firstLine[frameSize.height/2 - 2] = buffer[0];
                         firstLine[frameSize.height/2 - 1] = x1;
                         secondLine[frameSize.height/2 - 2] = buffer[1];
                         secondLine[frameSize.height/2 - 1] = x2;
                    //resend all coordinates to gui
                    for(int i = 0; i < frameSize.height/2; i++)
                         gui.setCord(i, firstLine[i], yPoint[i], secondLine[i]);
                    //Thread Control
                    try
                         //how fast the road moves
                         Thread.sleep(5);
                    } catch (InterruptedException e)
                         System.out.println(Thread.currentThread() + " Interrupted");
     public static void main (String[] args)
          MyFrame frame = new MyFrame();               
          frame.setVisible(true);
          //start Logic Thread
          new GuiLogic();
          //set main Thread to infintley repaint GUI
          while(true)
               gui.repaint();
Gui.java
import javax.swing.JPanel;
import java.awt.*;
class Gui extends JPanel {
     int x1Pos[];
     int x2Pos[];
     int yPos[];
     int num;
     Polygon poly;
     Color color;
     public class Colorer implements  Runnable
          Thread t;
          public Colorer()
               t = new Thread(this, "Colorer");
               t.start();
          public void run()
               poly.addPoint(x1Pos[num-1], 0);
               poly.addPoint(x2Pos[num-1], 0);
               poly.addPoint(x1Pos[0], yPos[0]);
               poly.addPoint(x2Pos[0], yPos[0]);
               System.out.println("asdf");
     public Gui(int amount)
          num = amount;
          x1Pos = new int[amount];
          x2Pos = new int[amount];
          yPos = new int[amount];
          poly = new Polygon();
          new Colorer();
          color = Color.red;          
     public void setCord(int loc, int x1, int y, int x2)
          x1Pos[loc] = x1;
          yPos[loc] = y;
          x2Pos[loc] = x2;
     public void setColor(Color c)
          color = c;
     public void paintComponent(Graphics g)
          super.paintComponent(g);
          if(x1Pos != null && x2Pos != null && yPos != null )
               g.drawPolyline(x1Pos, yPos, num);
               g.drawPolyline(x2Pos, yPos, num);

Answer 1

Use an actual java.awt.geom.Path2D and Graphics2D.fill(Shape)? Probably the same advice as earlier (since Polygon is-a Shape as well) so if it doesn't work show that in a SSCCE.
Edit: because painting is more fun that making reports here is a SSCCE. BTW, the proper forum would be the AWT one.
import java.awt.*;
import java.awt.geom.Path2D;
import java.awt.geom.Path2D.Double;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class TestFillShape extends JPanel {
    public TestFillShape() {
        setBackground(Color.BLUE);
        setPreferredSize(new Dimension(400, 400));
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int thirdX = getWidth() / 3;
        int thirdY = getHeight() / 3;
        Double path = new Path2D.Double();
        path.moveTo(thirdX, 1);
        path.lineTo(1, thirdY);
        path.lineTo(thirdX, getHeight() - thirdY);
        path.lineTo(thirdX, getHeight() - 1);
        path.lineTo(getWidth() - thirdX, getHeight() - 1);
        path.lineTo(getWidth() - 1, getHeight() - thirdY);
        path.lineTo(getWidth() - thirdX, thirdY);
        path.lineTo(getWidth() - 1, 1);
        path.closePath();
        ((Graphics2D) g).setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        g.setColor(Color.RED);
        ((Graphics2D) g).fill(path);
        g.setColor(Color.YELLOW);
        ((Graphics2D) g).setStroke(new BasicStroke(2f, BasicStroke.CAP_ROUND,
                BasicStroke.JOIN_ROUND));
        ((Graphics2D) g).draw(path);
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.getContentPane().add(new TestFillShape());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
}