Make extras classes final, not intended for extension

src/main/java/robaho/net/httpserver/extras/ContentEncoding.java

@@ -5,7 +5,7 @@
 
 import com.sun.net.httpserver.Headers;
 
-public class ContentEncoding {
+public final class ContentEncoding {
 
     private static final String defaultCharset = StandardCharsets.ISO_8859_1.name();
 

src/main/java/robaho/net/httpserver/extras/FormParser.java

@@ -14,7 +14,7 @@
 /**
  * Parse url-encoded requests.
  */
-public class FormParser {
+public final class FormParser {
 
     // Sets the maximum count of accepted POST params - protection against Hash collision DOS attacks
     private static final int MAX_PARAMS = Integer.getInteger("robaho.net.httpserver.max_form_params", 1000); // 0 == no limit

src/main/java/robaho/net/httpserver/extras/MultipartFormParser.java

@@ -22,7 +22,7 @@
 /**
  * parse multipart form data
  */
-public class MultipartFormParser {
+public final class MultipartFormParser {
     /**
      * a multipart part.
      *

src/main/java/robaho/net/httpserver/extras/QueryParameters.java

@@ -6,7 +6,7 @@
 import java.util.LinkedList;
 import java.util.List;
 
-public class QueryParameters extends LinkedHashMap<String, List<String>> {
+public final class QueryParameters extends LinkedHashMap<String, List<String>> {
 
     /**
      * @param encoding a valid java character set name