When I tried to run a code, an error occurred. Please explain why error occurred and how to fix it, thanks.

Here is my code:

Code:
/* package whatever; // don't place package name! */
 
/* Name of the class has to be "Main" only if the class is public. */
import java.util.ArrayList;
class Demo
{
	public static void main(String[] args) {
		ArrayList<String>
...