```
import javax.Swing.JOPtionPane;
public class while looping {
 public static void main (String []args){
  String a= JOptionPane.ShowInputDialog("Please enter an Integer");
   int b=Integer.parseInt(a);
   int j=1;
   while(j<=b){
    j++;
    int k=1;
    while (k<j){
     System.out.print("*");
     k++;
    }
    System.out.println();
   }
  }
 }
} 

```

This is my program and when i run it it says that `javac: invalid flag:` while what does it mean?