int yCoord = x4*(x^4) + x3*(x^3) + x2*(x^2) + x1*(x^1) + x0*(x^0);

import java.awt.image.*;
import java.awt.*;
import javax.swing.*;
 
public class ImagePlotter extends JPanel
{
	private Graphics2D g2d;
 
	private int[] xPoints;
	private int[] yPoints;
	private int[] coeff;
 
	public ImagePlotter(int coeff)
	{
		setPreferredSize(new Dimension(300,300));
 
		this.xPoints = new int[301];
		this.yPoints = new int[301];
		this.coeff = new int[coeff];
 
	}
	public void paintComponent(Graphics g)
	{
	 	g2d = (Graphics2D)g;
 
		g2d.setColor(Color.red);
		g2d.drawLine(150,0,150,300);
		g2d.drawLine(0,150,300,150);
 
/*drawing of the polynomial starts here, but since numbers are really big you
need to give smaller numbers in order to make it sense.
also this is not a very good way to give static numbers like 150 and 300 here
because when you make it full screen, it looks very odd,
*/
		for (int i=0; i<=300; i++)
		{
//this commentted part doesn't work...
/*		xPoints[i] = i - 150;
		yPoints[i] = fOfX(i - 150);
		g2d.drawPolyline(xPoints,yPoints,xPoints.length);*/
			int y=fOfX(i-150);
			g2d.drawLine(i,150,i,150-y);
		}
	}
 
	public int fOfX(int x)
	{
		int yCoord = 0;
		for (int i=0; i<coeff.length;i++) {
			yCoord += coeff[i] * (int)Math.pow((double)x,(double)i);
		}
		return yCoord;
	}
 
//Coefficient Setter
	public void setCoeff(int coeffNumber,int value) {
		coeff[coeffNumber] = value;
	}
}

import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
 
public class RoboPlot extends JFrame implements ChangeListener
{
	JSlider[] numberSlider1;
 
	JTabbedPane tabbedPane;
 
	ImagePlotter ip;
 
	//our constant values
	static final int root = 5; //number of roots of the polynomial
 
	public RoboPlot()
	{
//creates an imagePlotter with roots
		ip = new ImagePlotter(root);
		tabbedPane = new JTabbedPane();
 
		JPanel tab1Panel = new JPanel();
		tab1Panel.setBackground(Color.white);
		tabbedPane.addTab("Line 1", tab1Panel);
/*you can make this max and min constant so you can use them outside the constructor
for checking or something like that.
*/
		int max = 20;
		int min = -20;
		int init = 0;
 
		numberSlider1 = new JSlider[root];
		JLabel[] lblCoef = new JLabel[root];
/*
your first numberSlider is your first coefficients and so on
*/
		for (int i=0; i<root;i++)
		{
			lblCoef[i] = new JLabel("     a(x)^" + i);
			numberSlider1[i] = new JSlider(min, max, init);
			numberSlider1[i].setMajorTickSpacing(5);
			numberSlider1[i].setMinorTickSpacing(1);
			numberSlider1[i].setPaintLabels(true);
			numberSlider1[i].setPaintTicks(true);
			numberSlider1[i].setSnapToTicks(true);
			numberSlider1[i].setBackground(Color.white);
			numberSlider1[i].addChangeListener(this);
			tab1Panel.add(lblCoef[i]);
			tab1Panel.add(numberSlider1[i]);
		}
 
		Container pane = getContentPane();
		pane.setLayout(new BorderLayout());
		setBackground(Color.white);
		pane.add(ip,BorderLayout.NORTH);
		pane.add(tabbedPane);
		setSize(300,620);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setTitle("RoboPlot");
		setContentPane(pane);
		setVisible(true);
 
	}
 
	public void stateChanged(ChangeEvent e)
	{
		for (int i=0; i<root;i++) {
			if (e.getSource() == numberSlider1[i]) {
				//the change event fired from ith slider...
				//so change its value for the plotter..
				ip.setCoeff(i,numberSlider1[i].getValue());
			}
		}
		ip.repaint();
	}
	public static void main(String[] args)
	{
	RoboPlot rp = new RoboPlot();
	}
}