Java Puzzler

NullVarArgs.java

public class NullVarArgs {

    public static void main(String... args) {

        // 1
        exec(null);

        // 2
        exec((String) null);

        // 3
        final String s = null;
        exec(s);
    }


    private static void exec(String... args) {
        System.out.println(args);
    }
}

Warning:(8, 14) java: non-varargs call of varargs method with inexact argument type for last parameter;
cast to java.lang.String for a varargs call
cast to java.lang.String[] for a non-varargs call and to suppress this warning