Merged planet Enum and HashMap (closes #39)

space-age/example.java

+import java.math.BigDecimal;
+
 public class SpaceAge {
 
     private enum Planet {
-        EARTH, MERCURY, VENUS, MARS, JUPITER, SATURN, URANUS, NEPTUNE
+        EARTH(1.0),
+        MERCURY(0.2408467),
+        VENUS(0.61519726),
+        MARS(1.8808158),
+        JUPITER(11.862615),
+        SATURN(29.447498),
+        URANUS(84.016846),
+        NEPTUNE(164.79132);
+
+        private final double relativeOrbitalPeriod;
+
+        Planet(double relativeOrbitalPeriod) {
+            this.relativeOrbitalPeriod = relativeOrbitalPeriod;
+        }
+
+        public double getRelativeOrbitalPeriod() {
+            return relativeOrbitalPeriod;
+        }
     }
 
-    private double seconds;
-
     private static final double EARTH_ORBITAL_PERIOD_IN_SECONDS = 31557600.0;
     private static final int PRECISION = 2;
-    private static final Map<Planet, Double> relativeOrbitalPeriods = new HashMap<>();
-
-    static {
-        relativeOrbitalPeriods.put(Planet.EARTH, 1.0);
-        relativeOrbitalPeriods.put(Planet.MERCURY, 0.2408467);
-        relativeOrbitalPeriods.put(Planet.VENUS, 0.61519726);
-        relativeOrbitalPeriods.put(Planet.MARS, 1.8808158);
-        relativeOrbitalPeriods.put(Planet.JUPITER, 11.862615);
-        relativeOrbitalPeriods.put(Planet.SATURN, 29.447498);
-        relativeOrbitalPeriods.put(Planet.URANUS, 84.016846);
-        relativeOrbitalPeriods.put(Planet.NEPTUNE, 164.79132);
-    }
+
+    private double seconds;
 
     public SpaceAge(double seconds) {
         this.seconds = seconds;
     }
 
     public double onEarth() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.EARTH));
+        return calculateAge(Planet.EARTH);
     }
 
     public double onMercury() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.MERCURY));
+        return calculateAge(Planet.MERCURY);
     }
 
     public double onVenus() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.VENUS));
+        return calculateAge(Planet.VENUS);
     }
 
     public double onMars() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.MARS));
+        return calculateAge(Planet.MARS);
     }
 
     public double onJupiter() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.JUPITER));
+        return calculateAge(Planet.JUPITER);
     }
 
     public double onSaturn() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.SATURN));
+        return calculateAge(Planet.SATURN);
     }
 
     public double onUranus() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.URANUS));
+        return calculateAge(Planet.URANUS);
     }
 
     public double onNeptune() {
-        return calculateAge(relativeOrbitalPeriods.get(Planet.NEPTUNE));
+        return calculateAge(Planet.NEPTUNE);
     }
 
-    private double calculateAge(double relativeOrbitalPeriod) {
-        double age = seconds / (EARTH_ORBITAL_PERIOD_IN_SECONDS * relativeOrbitalPeriod);
+    private double calculateAge(Planet planet) {
+        double age = seconds / (EARTH_ORBITAL_PERIOD_IN_SECONDS * planet.getRelativeOrbitalPeriod());
 
         return new BigDecimal(age).setScale(PRECISION, BigDecimal.ROUND_HALF_UP).doubleValue();
     }