classVehicle{privateintwheels；privatefloatweight；protectedVehicle(intwheels，floatweight){this。wheels=wheels；this。weight=weight。是普通的除号，即10/2=5。
编写java程序的注意事项：
大小写敏感：Java是大小写敏感的，这就意味着标识符Hello与hello是不同的。
类名：对于所有的类来说，类名的首字母应该大写。如果类名由若干单词组成，那么每个单词的首字母应该大写，例如 MyFirstJavaClass。
方法名：所有的方法名都应该以小写字母开头。如果方法名含有若干单词，则后面的每个单词首字母大写，例如myFirstJavaClass。
import java.awt.Color
import java.awt.Graphics
import java.awt.Graphics2D
import java.awt.Point
import java.awt.event.KeyAdapter
import java.awt.event.KeyEvent
import javax.swing.JFrame
import com.me.util.JFrameUtil
public class SwingCar extends JFrame {
private final int rect_Width = 80
private final int rect_Height = 50
private final int radius = 15
private final int arcAngle = 30
private Point p = new Point()
public SwingCar() {
setSize(500, 300)
setVisible(true)
setResizable(false)
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
JFrameUtil.toCenter(this)
p = new Point(getWidth() / 2, getHeight() / 2)
move()
}
@Override
public void paint(Graphics g) {
super.paint(g)
drawRect(p)
drawRolls(p)
g.drawLine(0,getHeight()/2+rect_Height/2+radius, getWidth(), getHeight()/2+rect_Height/2+radius)
}
public void drawRect(Point c) {
Graphics2D g = (Graphics2D) getGraphics()
g.setColor(Color.red)
g.drawRect((int) (c.getX() - rect_Width / 2),
(int) (c.getY() - rect_Height / 2), rect_Width, rect_Height)
g.setColor(Color.black)
g.drawLine((int) (c.getX() - rect_Width / 2)-50, (int) (c.getY() - rect_Height / 2)-rect_Height/2, (int) (c.getX() - rect_Width / 2), (int) (c.getY() - rect_Height / 2)+rect_Height/2)
g.setColor(Color.green)
g.fillOval((int) (c.getX() - rect_Width / 2)-50-2, (int) (c.getY() - rect_Height / 2)-rect_Height/2-2, 10, 10)
}
public void drawRolls(Point c) {
Graphics2D g = (Graphics2D) getGraphics()
g.setColor(Color.blue)
// first roll
g.fillOval((int) (c.getX() - rect_Width / 4 - radius), (int) (c.getY()
+ rect_Height / 2 - radius), radius * 2, radius * 2)
g.setColor(Color.green)
g.fillArc((int) (c.getX() - rect_Width / 4 - radius), (int) (c.getY()
+ rect_Height / 2 - radius), radius * 2, radius * 2,
calcAngle(c), arcAngle)
// second roll
g.setColor(Color.blue)
g.fillOval((int) (c.getX() + rect_Width / 4 - radius), (int) (c.getY()
+ rect_Height / 2 - radius), radius * 2, radius * 2)
g.setColor(Color.green)
g.fillArc((int) (c.getX() + rect_Width / 4 - radius), (int) (c.getY()
+ rect_Height / 2 - radius), radius * 2, radius * 2,
calcAngle(c), arcAngle)
}
public int calcAngle(Point c) {
Point center = new Point(getWidth() / 2, getHeight() / 2)
double distance = c.getX() - center.getX()
int angle = (int) (180 * distance / (Math.PI * radius))
return -angle
}
public void move() {
this.addKeyListener(new KeyAdapter() {
@Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
p.translate(2, 0)
} else if (e.getKeyCode() == KeyEvent.VK_LEFT) {
p.translate(-2, 0)
}
repaint()
}
})
}
public static void main(String[] args) {
SwingCar sc = new SwingCar()
}
}
