Improving first iteration by avoiding string creation as much as possible (#516)

- It avoids creating unnecessary Strings objects and handles with the station names with its djb2 hashes instead
- Initializes hashmaps with capacity and load factor
- Adds -XX:+AlwaysPreTouch

github_users.txt

@@ -52,3 +52,4 @@ gnmathur;Gaurav Mathur
 vemana;Subrahmanyam
 jincongho;Jin Cong Ho
 yonatang;Yonatan Graber
+adriacabeza;Adrià Cabeza