import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {
        System.out.println("--- 1 ---");
        f(null); // --> warning
        f((String) null);
        f((String[]) null);

        System.out.println("--- 2 ---");
        String s = null;
        f(s == null ? null : new String[] { s });
        s = "hello, world";
        f(s == null ? null : new String[] { s });

        System.out.println("--- 3 ---");
        f();
        f("hello");
        f("hello", "world");

        System.out.println("--- 4 ---");
        f(new String[0]);
        f(new String[] { "hello" });
        f(new String[] { "hello", "world" });
    }

    public static void f(String... s) {
        System.out.println(s == null ? "null" : (s.length + ", " + toString(s)));
    }

    private static String toString(String[] a) {
        String s = "[";
        for (int i = 0; i < a.length; i += 1) {
            s += a[i] == null ? "null" : ("'" + a[i] + "'");
            if (i < a.length - 1) {
                s += ", ";
            }
        }
        s += "]";
        return s; 
    }
}