Remove warnings in model package

Author: kelvinqian00

src/main/java/com/yetanalytics/xapi/model/Extensions.java

@@ -24,7 +24,7 @@
 @JsonSerialize(using = ExtensionSerializer.class)
 public class Extensions {
 
-    private Map<String,Object> extMap = new HashMap<String,Object>();
+    private Map<String,Object> extMap = new HashMap<>();
 
     public Extensions(Map<String, Object> input) {
         extMap = input;
@@ -65,9 +65,11 @@ public <T> T read(String key, String jsonPathExpression, Class<T> typeKey) {
             return (T) JsonPath.read(json, jsonPathExpression);
         } catch (PathNotFoundException e) {
             //TODO: logging framework
-            e.printStackTrace();
+            System.err.println("Path not found");
+            // e.printStackTrace();
         } catch (JsonProcessingException e) {
-            e.printStackTrace();
+            System.err.println("JSON cannot be processed");
+            // e.printStackTrace();
         }
         return null;
     }

src/main/java/com/yetanalytics/xapi/model/InteractionType.java

@@ -21,7 +21,7 @@ public enum InteractionType {
     NUMERIC("numeric"), 
     OTHER("other");
 
-    private String displayName;
+    private final String displayName;
 
     InteractionType(String displayName) {
         this.displayName = displayName;

src/main/java/com/yetanalytics/xapi/model/LangMap.java

@@ -20,7 +20,7 @@
 @JsonSerialize(using = LangMapSerializer.class)
 public class LangMap {
 
-    private HashMap<String,String> languageHashMap = new HashMap<String, String>();
+    private HashMap<String,String> languageHashMap = new HashMap<>();
 
     /**
      * Create a new langmap from a HashMap

src/main/java/com/yetanalytics/xapi/model/ObjectType.java

@@ -16,7 +16,7 @@ public enum ObjectType {
     AGENT("Agent"),
     GROUP("Group");
 
-    private String displayName;
+    private final String displayName;
 
     ObjectType(String displayName) {
         this.displayName = displayName;

src/test/java/com/yetanalytics/ModelTest.java

@@ -0,0 +1,45 @@
+package com.yetanalytics;
+
+import java.util.Set;
+
+import com.yetanalytics.xapi.model.Agent;
+
+import jakarta.validation.ConstraintViolation;
+import jakarta.validation.Validation;
+import jakarta.validation.Validator;
+import junit.framework.TestCase;
+
+public class ModelTest extends TestCase {
+    /*
+    public void testLangMap() {
+        HashMap<String, String> goodLangMap = new HashMap<>();
+        HashMap<String, String> badLangMap1 = new HashMap<>();
+        HashMap<String, String> badLangMap2 = new HashMap<>();
+        HashMap<String, String> badLangMap3 = new HashMap<>();
+
+        goodLangMap.put("en-US", "foobar");
+        badLangMap1.put("", "foobar");
+        badLangMap2.put("notValidTag", "foobar");
+        badLangMap3.put("en-US", "");
+
+        assertNotNull(new LangMap(goodLangMap));
+        assertNull(new LangMap(badLangMap1));
+        assertNull(new LangMap(badLangMap3));
+    }
+        */
+    
+    public void testAgent() {
+        Validator validator = Validation.buildDefaultValidatorFactory()
+                                .getValidator();
+
+        Agent agent = new Agent();
+        agent.setName("Foo");
+        agent.setMbox("mailto:foo@example.com");
+
+        assertEquals("mailto:foo@example.com", agent.getMbox());
+
+        Set<ConstraintViolation<Agent>> violations = validator.validate(agent);
+        assertTrue(violations.isEmpty());
+        System.out.println(violations);
+    }
+}