字体问题

import java.awt.Color;

import java.awt.Dimension;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.Toolkit;

import java.awt.event.MouseAdapter;

import java.awt.event.MouseEvent;

import javax.swing.JFrame;

public class DrawLine extends JFrame{

public DrawLine()

{

setTitle("DrawLineTest");

Toolkit kit =Toolkit.getDefaultToolkit();

Dimension screenSize = kit.getScreenSize();

double screenWidth =screenSize.getWidth();

double screenHeight = screenSize.getHeight();

setBounds((int)screenWidth/2-DEFAULT_WIDTH/2,(int)screenHeight/2-DEFAULT_HEIGHT/2,DEFAULT_WIDTH,DEFAULT_HEIGHT);

addMouseListener(new MouseAdapter(){

int orgX;

int orgY;

public void mousePressed(MouseEvent e)

{

orgX = e.getX();

orgY = e.getY();

}

public void mouseReleased(MouseEvent e)

{

Graphics g = getGraphics();

g.setColor(Color.ORANGE);

g.drawString("("+orgX+","+orgY+")",orgX ,orgY);

g.drawString("("+e.getX()+","+e.getY()+")", e.getX(), e.getY());

g.setFont(new Font("Serif",Font.ITALIC,70));

g.drawLine(orgX, orgY, e.getX(), e.getY());

}

});

setVisible(true);

setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

}

public static void main(String[] args)

{

// TODO Auto-generated method stub

new DrawLine();

}

private static final int DEFAULT_WIDTH =400;

private static final int DEFAULT_HEIGHT=350;

}

其中的字体设置没有成功，理论上应该可以，为什么运行的时候字体就没有效果呢？