issue #123: Make Facts#get method cast friendly

easy-rules-core/src/main/java/org/jeasy/rules/api/Facts.java

@@ -69,12 +69,14 @@ public class Facts implements Iterable<Map.Entry<String, Object>> {
     /**
      * Get a fact by name.
      *
-     * @param name of fact to get.
+     * @param name of the fact
+     * @param <T> type of the fact
      * @return the fact having the given name, or null if there is no fact with the given name
      */
-    public Object get(String name) {
+    @SuppressWarnings("unchecked")
+    public <T> T get(String name) {
         Objects.requireNonNull(name);
-        return facts.get(name);
+        return (T) facts.get(name);
     }
 
     /**

easy-rules-tutorials/src/main/java/org/jeasy/rules/tutorials/airco/AirConditioningRule.java

@@ -17,7 +17,7 @@ public class AirConditioningRule {
     @Action
     public void coolAir(Facts facts) {
         System.out.println("It is hot! cooling air..");
-        Integer temperature = (Integer) facts.get("temperature");
+        Integer temperature = facts.get("temperature");
         facts.put("temperature", temperature - 1);
     }
 

easy-rules-tutorials/src/main/java/org/jeasy/rules/tutorials/shop/AgeRule.java

@@ -36,13 +36,13 @@ public class AgeRule extends BasicRule {
 
     @Override
     public boolean evaluate(Facts facts) {
-        Person person = (Person) facts.get("person");
+        Person person = facts.get("person");
         return person.getAge() > ADULT_AGE;
     }
 
     @Override
     public void execute(Facts facts) {
-        Person person = (Person) facts.get("person");
+        Person person = facts.get("person");
         person.setAdult(true);
         System.out.printf("Person %s has been marked as adult", person.getName());
         System.out.println();

easy-rules-tutorials/src/main/java/org/jeasy/rules/tutorials/shop/AlcoholRule.java

@@ -34,13 +34,13 @@ public class AlcoholRule extends BasicRule {
 
     @Override
     public boolean evaluate(Facts facts) {
-        Person person = (Person) facts.get("person");
+        Person person = facts.get("person");
         return !person.isAdult();
     }
 
     @Override
     public void execute(Facts facts){
-        Person person = (Person) facts.get("person");
+        Person person = facts.get("person");
         System.out.printf("Shop: Sorry %s, you are not allowed to buy alcohol", person.getName());
         System.out.println();
     }