A JAVA Program:Bouncing ball with color change on collision with walls

In this program a ball is created which bounces back and forth and also changes its color on collision with the walls of the container.

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CODE:

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import java.awt.Graphics;
import java.util.Random;

import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JOptionPane;
class bounceball extends JPanel
{
    private static final int win_w=640;
    private static final int win_h=480;
    private float rad=100;// radius of the ball
    private float x=rad+50;
    private float y=rad+20;//center coordinates of the ball
    private float sx=4;
    private float sy=3;       //change in the coordinates(x and y)
    private static final int update_rate=30;//refresh of screen per second
    // Now constructor
    private Random r;
    private Color clr=Color.BLUE;
    public void set(Color c)
    {
        clr=c;
    }
    public Color get()
    {
        return clr;
    }
    public bounceball()
    {
        r=new Random();
        setPreferredSize(new Dimension(win_w,win_h));//size of the panel is set to
        //the size of the window
        Thread ballthread=new Thread(){
            public void run(){
                                while(true)
                                {
                                    x+=sx;
                                    y+=sy;
                                    //here we handle collision with the window walls
                                    //checking the horizontal collision
                                    if(x-rad<0)
                                    {  
                                        sx=-sx;//reverse the direction
                                        x=rad;
                                        set(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
                                      
                                    }
                                    else if(x+rad>win_w)
                                    {
                                        sx=-sx;
                                        x=win_w-rad;
                                        set(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
                                    }
                                    //checking the vertical collision
                                    if(y-rad<0)
                                    {
                                        sy=-sy;
                                        y=rad;
                                        set(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
                                    }
                                    else if(y+rad>win_h)
                                    {  
                                        sy=-sy;
                                        y=win_h-rad;
                                        set(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
                                    }
                                    repaint();
                                    try
                                    {
                                        Thread.sleep(1000/update_rate);
                                    }
                                    catch(InterruptedException e)
                                    {
                                        JOptionPane.showMessageDialog(null,"Please don't interrupt me while sleeping !","Disturbed",JOptionPane.ERROR_MESSAGE);
                                    }
                                }
                             }
                            };
        ballthread.start();//start the thread's execution      
    }
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.setColor(Color.BLACK);
        g.fillRect(0,0,win_w,win_h);
        g.setColor(get());
        g.fillOval((int)(x-rad),(int)(y-rad),(int)(2*rad),(int)(2*rad));
        g.setColor(Color.WHITE);
        String s=String.format("Position:[%3.0f,%3.0f]",x,y);
        g.drawString(s,20,40);
    }
    public static void main(String [] args)
    {
        JFrame jr=new JFrame("Bouncing ball.");
        bounceball ball=new bounceball();
        jr.add(ball);
        jr.setVisible(true);
        jr.setSize(650,500);
        jr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jr.pack();
    }
}

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OUTPUT:

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More on this at techcresendo.com

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A java program to print a shape using wired mesh

This program uses swing and Graphics class.All coding is straight forward and can be easily understood.You may need to create main method to use this.

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import javax.swing.JPanel;

import java.awt.Graphics;

public class Drawpanel4 extends JPanel
{
    public void paintComponent(Graphics g)
    {
        int width=getWidth();
        int height=getHeight();
        int stepx=width/15;
        int stepy=height/15;
        super.paintComponent(g);
        int x=0,y=0,i=0,j=0,k=0,l=0;
        while(i<15)
        {   
            g.drawLine(0,y,x,height);
            y+=stepy;
            x+=stepx;
            i++;
       
        }
        x=0;y=height;   
        while(j<15)
        {
            g.drawLine(0,y,x,0);
            y-=stepy;
            x+=stepx;
            j++;
        }
        x=width;y=0;
        while(k<15)
        {
            g.drawLine(width,y,x,height);
            y+=stepy;
            x-=stepx;
            k++;
        }
        y=height;x=width;
        while(l<15)
        {
            g.drawLine(width,y,x,0);
            x-=stepx;
            y-=stepy;
            l++;
        }
    }
}

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OUTPUT:

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Program in java to show file description

This program shows the full description of a file or directory such as name ,when modified , length etc.

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import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.Font;

import java.io.File;

import javax.swing.JFileChooser;

import javax.swing.JFrame;

import javax.swing.JOptionPane;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

import javax.swing.JTextField;

class FileDemonstration extends JFrame
{
    private JTextArea outarea;
    private JScrollPane scroll;
    public FileDemonstration()
    {
        super("Testing Class file..");
        outarea=new JTextArea();
        outarea.setFont(new Font("Serif",Font.BOLD,14));
        scroll=new JScrollPane(outarea);
        add(scroll,BorderLayout.CENTER);
        setSize(400,400);
        setVisible(true);
        analyzefiles();
    }
    private File getFileinf()
    {
        JFileChooser fc=new JFileChooser();
        fc.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
        int result=fc.showOpenDialog(this);
        if(result==JFileChooser.CANCEL_OPTION)
            System.exit(1);
           
        File fname=fc.getSelectedFile();
        if((fname==null) || (fname.getName().equals("")))
        {
            JOptionPane.showMessageDialog(this,"Invalid Name!","Invalid Name!",JOptionPane.ERROR_MESSAGE);
            System.exit(1);
        }
        return fname;
    }
    public void analyzefiles()
    {
        File name=getFileinf();
        if(name.exists())
        {
            outarea.setText(String.format("%s %s\n %s\n %s\n %s\n %s \n %s\n%s\n %s %s\n %s %s",
            name.getName(),"exists.",(name.isFile()?" is file.":"is not a file."),
            (name.isDirectory()?"is directory":"is not a directory"),(name.isAbsolute() ? " is absolute.":"is not absolute"),
            "Last Modified:",name.lastModified(),"Length",name.length(),"Path:",name.getPath(),"Absolute Path",name.getAbsolutePath(),
            "Parent",name.getParent()));
        }
        if(name.isDirectory())
        {
            String[] dir=name.list();
            outarea.append("\n\nDirectory content\n\n");
            for(String dirname:dir)
                outarea.append(dirname+"\n");
        }
        else
            {
                JOptionPane.showMessageDialog(this,name+"does not exits.","Error",JOptionPane.ERROR_MESSAGE);
            }
    }
}
class jfile
{
    public static void main(String args[])
    {
        FileDemonstration f=new FileDemonstration();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

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output:

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There is no guarantee that all of these codes may work because some of them my have been used already.

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