j9

/*

1. Write a Java program to create a thread for moving a ball inside a panel vertically. The
   ball should be created when the user clicks on the start button (Use Swing).
   */
   package com.mycompany.practical_slip;

import java.awt.;
import java.awt.event.ActionEvent;
import java.util.logging.;
import javax.swing.*;

class BallPanel extends JPanel
{
private int yDelta = 0;

@Override
protected void paintComponent(Graphics g) 
{
    super.paintComponent(g);
    g.setColor(Color.red);
    g.fillOval(175, yDelta, 50, 50);
    repaint();
}

void setBallPos(int y) {
    this.yDelta = y;
}

}

public class slip9_1
{
private Thread ballThread;
private BallPanel ballPanel;
private JFrame frame;
private JButton start;

slip9_1() 
{
    frame = new JFrame("Ball Movement App");
    frame.setSize(400, 400);
    
    ballPanel = new BallPanel();
    
    start = new JButton("Start");
    start.addActionListener((ActionEvent e) -> 
    {
        startBallMovement();
    });
    
    frame.setLayout(new BorderLayout());
    frame.add(ballPanel, BorderLayout.CENTER);
    frame.add(start, BorderLayout.SOUTH);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}

private void startBallMovement() 
{
    if(ballThread == null || !ballThread.isAlive()) 
    {
        ballThread = new Thread(() -> {
            moveBallVertically();
        });
        ballThread.start();
    }
}


private void moveBallVertically() 
{
    int y = 0;
    int dir = 1;
    while(true) 
    {
        try 
        {
            Thread.sleep(15);
        } catch (InterruptedException ex) 
        {
            Logger.getLogger(slip9_1.class.getName()).log(Level.SEVERE, null, ex);
        }
        
        y += 5 * dir;
        
        if(y > ballPanel.getHeight() - 50)
            dir = -1;
        
        if(y <= 0)
            dir = 1;
        
        ballPanel.setBallPos(y);
    }
}

public static void main(String[] args) 
{
    new slip9_1();
}

}