class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            var s1 = new string("yyy");
            var s2 = new string("yyy");

            var s3 = new StringBuilder("yyy");
            var s4 = new StringBuilder("yyy");
            Console.WriteLine("object.ReferenceEquals(s1, s2): " + object.Equals(s1, s2));
            Console.WriteLine("object.ReferenceEquals(s3, s4): " + object.Equals(s3, s4));
            Console.WriteLine("s1 == s2: " + (s1.GetHashCode() + "  " + s2.GetHashCode()));
            Console.WriteLine("s1 == s2: " + (s1.GetHashCode() + " "  + s2.GetHashCode()) + " " + s1.Equals(s2));
            Console.WriteLine("s3 == s4: " + (s3.GetHashCode() + " " + s4.GetHashCode())  + " " + s3.Equals(s4));

            AutoResetEvent autoResetEvent = new AutoResetEvent(false);
            Console.ReadKey();
        }
    }