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.
Fixes #4911.

changelog.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ### Changed
 - [[#4634] Use Aliases in GraphQL Error Path](https://github.com/ballerina-platform/ballerina-standard-library/issues/4634)
+- [[#4911] Make some of the Java classes proper utility classes](https://github.com/ballerina-platform/ballerina-standard-library/issues/4911)
 
 ## [1.10.0] - 2023-09-18
 

commons/src/main/java/io/ballerina/stdlib/graphql/commons/utils/TypeUtils.java

@@ -24,7 +24,9 @@
 /**
  * Utility class for Ballerina GraphQL schema types.
  */
-public class TypeUtils {
+public final class TypeUtils {
+
+    private TypeUtils() {}
 
     private static final String UNICODE_REGEX = "\\\\(\\\\*)u\\{([a-fA-F0-9]+)\\}";
     private static final Pattern UNICODE_PATTERN = Pattern.compile(UNICODE_REGEX);

commons/src/main/java/io/ballerina/stdlib/graphql/commons/utils/Utils.java

@@ -37,7 +37,9 @@
 /**
  * Utility class to validate GraphQL package services and symbols.
  */
-public class Utils {
+public final class Utils {
+
+    private Utils () {}
 
     public static final String PACKAGE_NAME = "graphql";
     public static final String SUBGRAPH_SUB_MODULE_NAME = "graphql.subgraph";

native/src/main/java/io/ballerina/stdlib/graphql/runtime/client/QueryExecutor.java

@@ -30,7 +30,9 @@
 /**
  * This class is used to execute a GraphQL document using the Ballerina GraphQL client.
  */
-public class QueryExecutor {
+public final class QueryExecutor {
+
+    private QueryExecutor () {}
 
     /**
      * Executes the GraphQL document when the corresponding Ballerina remote operation is invoked.