This program uses several laws of physics to simulate cannonball motion. The motion formula utilizes the
Math class (
sin and
cos methods). The calculation is not highly accurate. It only takes into account the velocity of the cannonball (max 100 m/s), the launch angle (max 45 degrees), and gravitational force. However it should be enough to create a simple animation.
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113 | import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class SinCos extends JFrame{
private JTextField tf=null;
private JTextField tf2=null;
private JButton b=null;
private JPanel pmain=null;
private boolean shot=false;
private double posx=0;
private double posy=0;
private CannonBall cb=null;
public SinCos(){
super("CannonBall");
setSize(1100,400);
tf=new JTextField();
tf.setColumns(10);
tf2=new JTextField();
tf2.setColumns(10);
b=new JButton("Shoot!");
b.addActionListener(new ButtonHandler());
JPanel ptop=new JPanel();
ptop.setLayout(new FlowLayout());
ptop.add(tf);
ptop.add(tf2);
ptop.add(b);
pmain=new PanelDraw();
pmain.setPreferredSize(new Dimension(1100,300));
setLayout(new BorderLayout());
add("North",ptop);
add("Center",pmain);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
show();
}
class PanelDraw extends JPanel{
public void paintComponent(Graphics g){
//g.clearRect(0,0,1100,350);
super.paintComponent(g);
Graphics2D g2=(Graphics2D)g;
g2.setColor(Color.BLACK);
if(shot==true){
g2.fillOval((int)posx,pmain.getHeight()-(int)posy,10,10);
}
}
}
class ButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
if(e.getSource()==b){
cb=new CannonBall();
Thread t=new Thread(cb);
t.start();
}
}
}
class CannonBall implements Runnable{
double t=0;
double vx=0;
double vy=0;
public CannonBall(){
shot=true;
double deg=Double.valueOf(tf.getText()).doubleValue();
if(deg>45){
return;
}
double rad=deg*Math.PI/180;
double vel=Double.valueOf(tf2.getText()).doubleValue();
if(vel>100){
return;
}
//dist=2*Math.pow(vel,2)*Math.sin(rad)*Math.cos(rad)/9.8;
t=2*vel*Math.sin(rad)/9.8;
vx=vel*Math.cos(rad);
vy=vel*Math.sin(rad);
}
public void run(){
for(int i=0;i<=Math.ceil(t);i++){
double x=vx*i;
double y=(vy*i)-(0.5*9.8*Math.pow(i,2));
posx=x;
posy=y;
try{
Thread.currentThread().sleep(1000);
}catch(Exception ex){
}
pmain.repaint();
}
shot=false;
}
}
public static void main(String[] args){
new SinCos();
}
}
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