rename packages lower case

src/main/java/server/Era.java

@@ -0,0 +1,19 @@
+package server;
+
+public enum Era {
+    I,
+    II,
+    III,
+    FINAL;
+
+
+    public Era next() {
+        Era[] eras = values();
+        // Calcola l'indice del prossimo elemento
+        int nextOrdinal = this.ordinal() + 1;
+        if (nextOrdinal < eras.length) {
+            return eras[nextOrdinal];
+        }
+        return this;
+    }
+}