Make some Java classes proper utilities

Made the design cleaner by marking Java classes as `final`
and explicitly declaring their default constructors as `private`.
This change makes the code coverage reports more accurate.
Closes #5075.

changelog.md

@@ -3,6 +3,9 @@ This file contains all the notable changes done to the Ballerina SOAP package th
 
 ## [Unreleased]
 
+### Changed
+- [Make some of the Java classes proper utility classes](https://github.com/ballerina-platform/ballerina-standard-library/issues/5075)
+
 ## [0.8.0] - 2023-10-16
 
 ### Added

native/src/main/java/org/wssec/WsSecurity.java

@@ -56,7 +56,9 @@
 import static org.wssec.WsSecurityUtils.convertDocumentToString;
 import static org.wssec.WsSecurityUtils.setUTChildElements;
 
-public class WsSecurity {
+public final class WsSecurity {
+
+    private WsSecurity() {}
 
     public static Object applyUsernameTokenPolicy(BObject wsSecHeader, BString username,
                                                   BString password, BString passwordType) {

native/src/main/java/org/wssec/WsSecurityUtils.java

@@ -59,7 +59,9 @@
 import static org.wssec.Constants.XML_DS_NS;
 import static org.wssec.Constants.XML_ENC_NS;
 
-public class WsSecurityUtils {
+public final class WsSecurityUtils {
+
+    private WsSecurityUtils() {}
 
     public static void buildSignature(RequestData reqData, WSSecSignature sign) throws Exception {
         List<WSEncryptionPart> parts = new ArrayList<>(1);