Fix javadoc

Author: justin-tay

src/main/java/com/networknt/schema/DisallowUnknownJsonMetaSchemaFactory.java

@@ -31,6 +31,11 @@ private static class Holder {
         private static DisallowUnknownJsonMetaSchemaFactory INSTANCE = new DisallowUnknownJsonMetaSchemaFactory();
     }
 
+    /**
+     * Gets the instance of {@link DisallowUnknownJsonMetaSchemaFactory}.
+     * 
+     * @return the json meta schema factory
+     */
     public static DisallowUnknownJsonMetaSchemaFactory getInstance() {
         return Holder.INSTANCE;
     }

src/main/java/com/networknt/schema/DisallowUnknownKeywordFactory.java

@@ -36,6 +36,11 @@ private static class Holder {
         private static DisallowUnknownKeywordFactory INSTANCE = new DisallowUnknownKeywordFactory();
     }
 
+    /**
+     * Gets the instance of {@link DisallowUnknownKeywordFactory}.
+     *
+     * @return the keyword factory
+     */
     public static DisallowUnknownKeywordFactory getInstance() {
         return Holder.INSTANCE;
     }