>>249
Graphics2D使うとペンの太さを設定できる。

たとえばこんなかんじ。
import java.awt.*;
import java.awt.event.*;
public class MouseDraw extends Frame {
private int x;
private int y;
private Graphics2D grp;
public MouseDraw() {
addMouseMotionListener(new MouseMotionAdapter(){
public void mouseDragged(MouseEvent e){
grp.drawLine(x, y, e.getX(), e.getY());
x = e.getX();
y = e.getY();
}
});
setSize(400,400);
show();
grp = (Graphics2D)getGraphics();
grp.setStroke(new BasicStroke(5, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
}
public static void main(String[] args) {
MouseDraw test = new MouseDraw();
}
}