How can I get these java line algorithms working?

How can I get these java line algorithms working?

I'm trying to demonstrate Bresenham's line algorithm as opposed to a less
sophisticated approach. I'm very new to programming and I'm sure my
problems are elementary, but a solution and an explanation would be hugely
helpful. Thanks!
This first block of code comes straight out of my book.
import java.awt.*;
import javax.swing.*;
public class lines extends JPanel {
int deltaX;
int deltaY;
int DY2;
int DX2;
int Di;
public void basic(int x1, int y1, int x2, int y2, Graphics
g){
int deltaX = x2-x1;
int deltaY = y2-y1;
float m = (float)deltaY/(float)deltaX;
float c = y1 - (m*x1);
for (int x=x1; x<x2; x++){
float floatY = (m*x) + c;
int y = Math.round(floatY);
g.drawLine(x,y,x,y);
}
}
public void brz(int x1, int y1, int x2, int y2,
Graphics g){
deltaX = x2-x1;
deltaY = y2-y1;
DY2 = 2* deltaY;
DX2 = 2* deltaX;
Di = DY2 - deltaX;
int x = x1;
int y = y1;
int prevy;
while (x<x2) {
x++;
prevy = y;
if (Di > 0){
y++;
}
g.drawLine(x,y,x,y);
Di = Di + DY2 - (DX2 * (y - prevy));
}
}
public void paintComponent(Graphics g){
basic(10,10,40,30,g);
basic(10,10,40,90,g);
brz(50,50,150,60,g);
brz(50,50,150,120,g);
brz(50,50,150,140,g);
}
It told me I need a main class, so I added this bit:
public static void main(String[] args) {
paintComponent(Graphics g);
}
Now it's giving me this:
lines.java:15: ')' expected paintComponent(Graphics g);
lines.java:15: illegal start of expression paintComponent(Graphics g);