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 #4926.

changelog.md

@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Changed
+- [Make some of the Java classes proper utility classes](https://github.com/ballerina-platform/ballerina-standard-library/issues/4926)
+
 ## [1.9.1] - 2023-10-12
 
 ### Fixed

compiler-plugin/src/main/java/io/ballerina/stdlib/udp/compiler/Utils.java

@@ -39,7 +39,9 @@
 /**
  * Compiler-plugin utility class.
  */
-public class Utils {
+public final class Utils {
+
+    private Utils() {}
 
     public static final String NODE_LOCATION = "node.location";
     public static final String LS = System.lineSeparator();

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

@@ -21,7 +21,9 @@
 /**
  * Constant variable for udp related operations.
  */
-public class Constants {
+public final class Constants {
+
+    private Constants() {}
 
     // Constant related to ballerina Datagram record
     public static final String DATAGRAM_RECORD = "Datagram";

native/src/main/java/io/ballerina/stdlib/udp/Dispatcher.java

@@ -39,7 +39,9 @@
 /**
  * Dispatch async methods.
  */
-public class Dispatcher {
+public final class Dispatcher {
+
+    private Dispatcher() {}
 
     private static final Logger log = LoggerFactory.getLogger(Dispatcher.class);
 

native/src/main/java/io/ballerina/stdlib/udp/Utils.java

@@ -39,7 +39,9 @@
  *
  * @since 0.985.0
  */
-public class Utils {
+public final class Utils {
+
+    private Utils() {}
 
     /**
      * udp standard library package ID.

native/src/main/java/io/ballerina/stdlib/udp/nativeclient/Client.java

@@ -39,7 +39,9 @@
  *
  * @since 1.1.0
  */
-public class Client {
+public final class Client {
+
+    private Client() {}
 
     public static Object init(Environment env, BObject client, BMap<BString, Object> config) {
         final Future balFuture = env.markAsync();

native/src/main/java/io/ballerina/stdlib/udp/nativeclient/ConnectClient.java

@@ -39,7 +39,9 @@
  *
  * @since 1.1.0
  */
-public class ConnectClient {
+public final class ConnectClient {
+
+    private ConnectClient() {}
 
     public static Object init(Environment env, BObject client, BString remoteHost,
                               int remotePort, BMap<BString, Object> config) {

native/src/main/java/io/ballerina/stdlib/udp/nativelistener/Caller.java

@@ -36,7 +36,9 @@
 /**
  * Native function implementations of the UDP Caller.
  */
-public class Caller {
+public final class Caller {
+
+    private Caller() {}
 
     public static Object sendBytes(Environment env, BObject caller, BArray data) {
         final Future callback = env.markAsync();

native/src/main/java/io/ballerina/stdlib/udp/nativelistener/Listener.java

@@ -38,7 +38,9 @@
 /**
  * Native function implementations of the UDP Listener.
  */
-public class Listener {
+public final class Listener {
+    private Listener() {}
+
     private static final Logger log = LoggerFactory.getLogger(Client.class);
 
     public static Object init(BObject listener, int localPort, BMap<BString, Object> config) {

test-utils/src/main/java/io/ballerina/stdlib/udp/testutils/MockServerUtils.java

@@ -32,7 +32,9 @@
 /**
  * This UDP server udp will use to mock the backend server.
  */
-public class MockServerUtils {
+public final class MockServerUtils {
+
+    private MockServerUtils() {}
 
     private static MockUdpServer mockUdpServer;