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

calculate_average_adriacabeza.sh

@@ -16,6 +16,6 @@
 #
 
 
-JAVA_OPTS="-XX:+UseStringDeduplication -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC"
+JAVA_OPTS="-XX:+UseStringDeduplication -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -XX:+AlwaysPreTouch"
 java --enable-preview  -classpath target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_adriacabeza