Try making java 6 & old version javadoc generator compatible

src/main/java/org/json/JSONDuplicateKeyStrategy.java

@@ -6,7 +6,7 @@ package org.json;
  */
 public enum JSONDuplicateKeyStrategy {
     /**
-     * The default value. And this is the way it used to be in the previous versions.<br/>
+     * The default value. And this is the way it used to be in the previous versions.<br>
      * The JSONParser will throw an {@link JSONException} when meet duplicate key.
      */
     THROW_EXCEPTION,

src/main/java/org/json/JSONObject.java

@@ -256,7 +256,7 @@ public class JSONObject {
 
                         case MERGE_INTO_ARRAY:
                             if (mergedKeys == null) {
-                                mergedKeys = new ArrayList<>();
+                                mergedKeys = new ArrayList<String>();
                             }
 
                             Object current = this.get(key);