BouncingBall.java

public class BouncingBall {

    public static void main(String[] args) throws InterruptedException {
       final int ROWS = 10;
       final int COLS = 20;
       int ballRow = 0;
       int ballCol = 0;
       int velocityRow = 1;
       int velocityCol = 1;
 
       while (true) {
          // Clear console (simulate by printing many new lines)
          for (int i = 0; i < 50; i++) {
             System.out.println();
          }
 
          // Print the grid with ball
          for (int r = 0; r < ROWS; r++) {
             for (int c = 0; c < COLS; c++) {
                if (r == ballRow && c == ballCol) {
                   System.out.print("*");
                } else {
                   System.out.print(".");
                }
             }
             System.out.println();
          }
 
          // Update position
          ballRow += velocityRow;
          ballCol += velocityCol;
 
          // Bounce on wall
          if (ballRow == 0 || ballRow == ROWS - 1) {
             velocityRow *= -1;
          }
          if (ballCol == 0 || ballCol == COLS - 1) {
             velocityCol *= -1;
          }
 
          Thread.sleep(100); // Delay for animation
       }
    }
 }