Query: The import java.util.ArrayList cannot be resolved Java

Hello All, I am facing some issues while I am trying to run this java program in vscode on online compiler but it shows an error on the 2nd line (The import java.util.ArrayList cannot be resolved Java(268435846)) and 6th line. But it gives correct output in an online compiler. Any suggestions?

import java.util.List;
import java.util.ArrayList;
import java.util.Collection;
class main {
    public static void main(String args) {
       ArrayList al = new ArrayList();
       al.add(100);
       al.add("String");  
       System.out.println(al);
   }
}