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 #4929.

changelog.md

@@ -3,6 +3,11 @@ This file contains all the notable changes done to the Ballerina Constraint pack
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Changed
+- [Make some of the Java classes proper utility classes](https://github.com/ballerina-platform/ballerina-standard-library/issues/4929)
+
 ## [1.2.0] - 2023-06-01
 
 ### Added

compiler-plugin-tests/src/test/java/io/ballerina/stdlib/constraint/compiler/CompilerPluginTestConstants.java

@@ -21,7 +21,9 @@
 /**
  * The constants related to compiler plugin tests.
  */
-public class CompilerPluginTestConstants {
+public final class CompilerPluginTestConstants {
+
+    private CompilerPluginTestConstants() {}
 
     static final String ANNOTATION_TAG_INT = "Int";
     static final String ANNOTATION_TAG_FLOAT = "Float";

compiler-plugin-tests/src/test/java/io/ballerina/stdlib/constraint/compiler/CompilerPluginTestUtils.java

@@ -38,7 +38,9 @@
 /**
  * Utility functions related to compiler plugins tests.
  */
-public class CompilerPluginTestUtils {
+public final class CompilerPluginTestUtils {
+
+    private CompilerPluginTestUtils() {}
 
     private static final Path RESOURCE_DIRECTORY = Paths.get("src", "test", "resources", "ballerina_sources")
             .toAbsolutePath();

compiler-plugin/src/main/java/io/ballerina/stdlib/constraint/compiler/Constants.java

@@ -21,7 +21,9 @@
 /**
  * The constants related to compiler plugin.
  */
-public class Constants {
+public final class Constants {
+
+    private Constants() {}
 
     public static final String PACKAGE_NAME = "ballerina";
     public static final String MODULE_NAME = "constraint";

compiler-plugin/src/main/java/io/ballerina/stdlib/constraint/compiler/ConstraintCompilerPluginUtils.java

@@ -51,7 +51,9 @@
 /**
  * The compiler plugin utility functions.
  */
-public class ConstraintCompilerPluginUtils {
+public final class ConstraintCompilerPluginUtils {
+
+    private ConstraintCompilerPluginUtils() {}
 
     private static final ConstraintCompatibilityMatrix matrix = new ConstraintCompatibilityMatrix();
 

native/src/main/java/io/ballerina/stdlib/constraint/Constants.java

@@ -24,7 +24,9 @@
 /**
  * Constants related to constraint module.
  */
-public class Constants {
+public final class Constants {
+
+    private Constants() {}
 
     public static final String PREFIX_RECORD_FIELD = "$field$";
     public static final String ANNOTATION_RECORD_REGEX = "^ballerina/constraint:[0-9]+:.+";

native/src/main/java/io/ballerina/stdlib/constraint/ErrorUtils.java

@@ -35,7 +35,9 @@
 /**
  * Utility functions related to errors.
  */
-public class ErrorUtils {
+public final class ErrorUtils {
+
+    private ErrorUtils() {}
 
     private static final String UNEXPECTED_ERROR_MESSAGE = "Unexpected error found due to typedesc and value mismatch.";
     private static final String TYPE_CONVERSION_ERROR_MESSAGE = "Type conversion failed due to typedesc and value " +