public class Main – defines the class Main.

public static void main(String[] args) – main method where program execution starts.

for (int i = 1; i <= 10; i++) – a for loop that runs from 1 to 10, printing each number.

int countdown = 3; – initializes a variable countdown with the value 3.

while (countdown > 0) – a while loop that continues as long as countdown is greater than 0.

System.out.println("Countdown: " + countdown); – prints the current countdown number.

countdown--; – decreases countdown by 1 each loop iteration.

System.out.println("Go!"); – prints “Go!” after the countdown finishes.