Make Java classes final if possible

Also add private no-arg constructors for classes that aren't meant to be instantiated.
2026-03-21 08:39:09 +01:00 · 2024-04-27 20:31:57 -07:00
parent ae69e4776f
commit e49a36e318
57 changed files with 89 additions and 70 deletions
--- a/pkl-core/src/main/java/org/pkl/core/BufferedLogger.java
+++ b/pkl-core/src/main/java/org/pkl/core/BufferedLogger.java
@@ -16,7 +16,7 @@
 package org.pkl.core;

 /** A logger that keeps messages locally and can return them. */
-public class BufferedLogger implements Logger {
+public final class BufferedLogger implements Logger {

  private final StringBuilder builder = new StringBuilder();
  private final Logger logger;
--- a/pkl-core/src/main/java/org/pkl/core/Loggers.java
+++ b/pkl-core/src/main/java/org/pkl/core/Loggers.java
@@ -21,6 +21,8 @@ import java.io.PrintWriter;
 /** Predefined {@link Logger}s. */
@SuppressWarnings("unused")
 public final class Loggers {
+  private Loggers() {}
+
  /** Returns a logger that discards log messages. */
  public static Logger noop() {
    return new Logger() {
--- a/pkl-core/src/main/java/org/pkl/core/ModuleSource.java
+++ b/pkl-core/src/main/java/org/pkl/core/ModuleSource.java
@@ -27,7 +27,7 @@ import org.pkl.core.util.Nullable;
 * <p>Create a new module source via {@link #create(URI, String)}, or one of the various helper
 * factory methods.
 */
-public class ModuleSource {
+public final class ModuleSource {
  public static ModuleSource create(URI uri, @Nullable String text) {
    return new ModuleSource(uri, text);
  }
--- a/pkl-core/src/main/java/org/pkl/core/Release.java
+++ b/pkl-core/src/main/java/org/pkl/core/Release.java
@@ -27,7 +27,7 @@ import java.util.Set;
 * Information about the Pkl release that the current program runs on. This class is the Java
 * equivalent of standard library module {@code pkl.release}.
 */
-public class Release {
+public final class Release {
  private static final String SOURCE_CODE_HOMEPAGE = "https://github.com/apple/pkl/";
  private static final String DOCUMENTATION_HOMEPAGE = "https://pkl-lang.org/main/";

--- a/pkl-core/src/main/java/org/pkl/core/RendererException.java
+++ b/pkl-core/src/main/java/org/pkl/core/RendererException.java
@@ -15,7 +15,7 @@
 */
 package org.pkl.core;

-public class RendererException extends RuntimeException {
+public final class RendererException extends RuntimeException {
  public RendererException(String message) {
    super(message);
  }
--- a/pkl-core/src/main/java/org/pkl/core/SecurityManagerException.java
+++ b/pkl-core/src/main/java/org/pkl/core/SecurityManagerException.java
@@ -20,7 +20,7 @@ package org.pkl.core;
 *
 * <p>{@link SecurityManagerException#getMessage()} is passed to users when errors arise.
 */
-public class SecurityManagerException extends Exception {
+public final class SecurityManagerException extends Exception {
  public SecurityManagerException(String message) {
    super(message);
  }
--- a/pkl-core/src/main/java/org/pkl/core/ast/VmModifier.java
+++ b/pkl-core/src/main/java/org/pkl/core/ast/VmModifier.java
@@ -22,6 +22,8 @@ import org.pkl.core.runtime.VmExceptionBuilder;
 import org.pkl.core.runtime.VmSet;

 public final class VmModifier {
+  private VmModifier() {}
+
  // user-facing modifiers

  public static final int ABSTRACT = 0x1;
--- a/pkl-core/src/main/java/org/pkl/core/ast/builder/ImportsAndReadsParser.java
+++ b/pkl-core/src/main/java/org/pkl/core/ast/builder/ImportsAndReadsParser.java
@@ -46,7 +46,7 @@ import org.pkl.core.util.Pair;
 *   <li>read expressions
 * </ul>
 */
-public class ImportsAndReadsParser
+public final class ImportsAndReadsParser
    extends AbstractAstBuilder<@Nullable List<Pair<String, SourceSection>>> {

  /** Parses a module, and collects all imports and reads. */
@@ -69,7 +69,7 @@ public class ImportsAndReadsParser
  }

  @Override
-  public @Nullable List<Pair<String, SourceSection>> visitModuleExtendsOrAmendsClause(
+  public List<Pair<String, SourceSection>> visitModuleExtendsOrAmendsClause(
      ModuleExtendsOrAmendsClauseContext ctx) {
    var importStr = doVisitSingleLineConstantStringPart(ctx.stringConstant().ts);
    var sourceSection = createSourceSection(ctx.stringConstant());
--- a/pkl-core/src/main/java/org/pkl/core/http/HttpClientInitException.java
+++ b/pkl-core/src/main/java/org/pkl/core/http/HttpClientInitException.java
@@ -19,7 +19,7 @@ package org.pkl.core.http;
 * Indicates that an error occurred while initializing an HTTP client. A common example is an error
 * reading or parsing a certificate.
 */
-public class HttpClientInitException extends RuntimeException {
+public final class HttpClientInitException extends RuntimeException {
  public HttpClientInitException(String message) {
    super(message);
  }
--- a/pkl-core/src/main/java/org/pkl/core/http/LazyHttpClient.java
+++ b/pkl-core/src/main/java/org/pkl/core/http/LazyHttpClient.java
@@ -29,7 +29,7 @@ import javax.annotation.concurrent.ThreadSafe;
 * send.
 */
@ThreadSafe
-class LazyHttpClient implements HttpClient {
+final class LazyHttpClient implements HttpClient {
  private final Supplier<HttpClient> supplier;
  private final Object lock = new Object();

--- a/pkl-core/src/main/java/org/pkl/core/module/FileResolver.java
+++ b/pkl-core/src/main/java/org/pkl/core/module/FileResolver.java
@@ -25,7 +25,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;

-public class FileResolver {
+public final class FileResolver {
  private FileResolver() {}

  public static List<PathElement> listElements(URI baseUri) throws IOException {
--- a/pkl-core/src/main/java/org/pkl/core/module/ModulePathResolver.java
+++ b/pkl-core/src/main/java/org/pkl/core/module/ModulePathResolver.java
@@ -38,7 +38,7 @@ import org.pkl.core.util.LateInit;
 * <p>NOTE: Do not initialize two resolvers for the same jar or zip file. Instead, share the same
 * resolver for that jar or zip file.
 */
-public class ModulePathResolver implements AutoCloseable {
+public final class ModulePathResolver implements AutoCloseable {
  private final Iterable<Path> modulePath;

  private final Object lock = new Object();
--- a/pkl-core/src/main/java/org/pkl/core/module/PathElement.java
+++ b/pkl-core/src/main/java/org/pkl/core/module/PathElement.java
@@ -80,7 +80,7 @@ public class PathElement {
    return "PathElement{" + "name='" + name + '\'' + ", isDirectory=" + isDirectory + '}';
  }

-  public static class TreePathElement extends PathElement {
+  public static final class TreePathElement extends PathElement {
    private final EconomicMap<String, TreePathElement> children = EconomicMaps.create();

    public TreePathElement(String name, boolean isDirectory) {
--- a/pkl-core/src/main/java/org/pkl/core/module/ProjectDependenciesManager.java
+++ b/pkl-core/src/main/java/org/pkl/core/module/ProjectDependenciesManager.java
@@ -35,7 +35,7 @@ import org.pkl.core.runtime.VmExceptionBuilder;
 import org.pkl.core.util.EconomicMaps;
 import org.pkl.core.util.json.Json.JsonParseException;

-public class ProjectDependenciesManager {
+public final class ProjectDependenciesManager {
  public static final String PKL_PROJECT_FILENAME = "PklProject";

  public static final String PKL_PROJECT_DEPS_FILENAME = "PklProject.deps.json";
--- a/pkl-core/src/main/java/org/pkl/core/packages/DependencyMetadata.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/DependencyMetadata.java
@@ -70,7 +70,7 @@ import org.pkl.core.util.json.JsonWriter;
 */
@SuppressWarnings({"JavadocLinkAsPlainText", "unused"})
 // incorrectly thinks link within sample metadata is a JavaDoc link
-public class DependencyMetadata {
+public final class DependencyMetadata {

  public static DependencyMetadata parse(String input) throws JsonParseException {
    var parsed = Json.parseObject(input);
--- a/pkl-core/src/main/java/org/pkl/core/packages/PackageAssetUri.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/PackageAssetUri.java
@@ -25,7 +25,7 @@ import org.pkl.core.util.ErrorMessages;
 * The canonical URI of an asset within a package, i.e., a package URI with a fragment path. For
 * example, {@code package://example.com/my/package@1.0.0#/my/module.pkl}
 */
-public class PackageAssetUri {
+public final class PackageAssetUri {
  private final URI uri;
  private final PackageUri packageUri;
  private final Path assetPath;
--- a/pkl-core/src/main/java/org/pkl/core/packages/PackageLoadError.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/PackageLoadError.java
@@ -17,7 +17,7 @@ package org.pkl.core.packages;

 import org.pkl.core.util.ErrorMessages;

-public class PackageLoadError extends RuntimeException {
+public final class PackageLoadError extends RuntimeException {

  private final String messageName;
  private final Object[] arguments;
--- a/pkl-core/src/main/java/org/pkl/core/packages/PackageResolvers.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/PackageResolvers.java
@@ -60,7 +60,9 @@ import org.pkl.core.util.Nullable;
 import org.pkl.core.util.Pair;
 import org.pkl.core.util.json.Json.JsonParseException;

-class PackageResolvers {
+final class PackageResolvers {
+  private PackageResolvers() {}
+
  abstract static class AbstractPackageResolver implements PackageResolver {
    @GuardedBy("lock")
    private final EconomicMap<PackageUri, DependencyMetadata> cachedDependencyMetadata;
@@ -245,7 +247,7 @@ class PackageResolvers {
   *
   * <p>This gets used when the cache dir is not set.
   */
-  static class InMemoryPackageResolver extends AbstractPackageResolver {
+  static final class InMemoryPackageResolver extends AbstractPackageResolver {
    @GuardedBy("lock")
    private final EconomicMap<PackageUri, EconomicMap<String, ByteBuffer>> cachedEntries =
        EconomicMaps.create();
@@ -406,7 +408,7 @@ class PackageResolvers {
   * <p>Uses the built-in zip file system in {@link jdk.nio.zipfs} for reading files from the zip
   * archive.
   */
-  static class DiskCachedPackageResolver extends AbstractPackageResolver {
+  static final class DiskCachedPackageResolver extends AbstractPackageResolver {
    private final Path cacheDir;

    private final Path tmpDir;
--- a/pkl-core/src/main/java/org/pkl/core/packages/PackageUri.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/PackageUri.java
@@ -23,7 +23,7 @@ import org.pkl.core.util.ErrorMessages;
 import org.pkl.core.util.IoUtils;
 import org.pkl.core.util.Nullable;

-public class PackageUri {
+public final class PackageUri {
  private final URI uri;
  private final Version version;
  private final String pathWithoutVersion;
--- a/pkl-core/src/main/java/org/pkl/core/packages/PackageUtils.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/PackageUtils.java
@@ -20,7 +20,9 @@ import org.pkl.core.util.ErrorMessages;
 import org.pkl.core.util.json.Json.FormatException;
 import org.pkl.core.util.json.Json.JsonParseException;

-public class PackageUtils {
+public final class PackageUtils {
+  private PackageUtils() {}
+
  public static PackageUri parsePackageUriWithoutChecksums(Object obj)
      throws JsonParseException, URISyntaxException {
    if (!(obj instanceof String string)) {
--- a/pkl-core/src/main/java/org/pkl/core/parser/ErrorStrategy.java
+++ b/pkl-core/src/main/java/org/pkl/core/parser/ErrorStrategy.java
@@ -20,7 +20,7 @@ import org.antlr.v4.runtime.Parser;
 import org.antlr.v4.runtime.misc.IntervalSet;
 import org.pkl.core.parser.antlr.PklParser;

-class ErrorStrategy extends DefaultErrorStrategy {
+final class ErrorStrategy extends DefaultErrorStrategy {
  @Override
  protected void reportNoViableAlternative(Parser parser, NoViableAltException e) {
    var builder = new StringBuilder();
--- a/pkl-core/src/main/java/org/pkl/core/parser/LexParseException.java
+++ b/pkl-core/src/main/java/org/pkl/core/parser/LexParseException.java
@@ -67,7 +67,7 @@ public abstract class LexParseException extends RuntimeException {
    return this;
  }

-  public static class LexError extends LexParseException {
+  public static final class LexError extends LexParseException {
    public LexError(String message, int line, int column, int length) {
      super(message, line, column, length, Integer.MAX_VALUE);
    }
@@ -79,7 +79,7 @@ public abstract class LexParseException extends RuntimeException {
    }
  }

-  public static class IncompleteInput extends ParseError {
+  public static final class IncompleteInput extends ParseError {
    public IncompleteInput(String message, int line, int column, int length) {
      super(message, line, column, length, Integer.MAX_VALUE - 1);
    }
--- a/pkl-core/src/main/java/org/pkl/core/parser/Lexer.java
+++ b/pkl-core/src/main/java/org/pkl/core/parser/Lexer.java
@@ -23,7 +23,7 @@ import org.antlr.v4.runtime.*;
 import org.pkl.core.parser.antlr.PklLexer;
 import org.pkl.core.util.Nullable;

-public class Lexer {
+public final class Lexer {
  public static final Set<Integer> KEYWORD_TYPES;
  public static final Set<String> KEYWORD_NAMES;

--- a/pkl-core/src/main/java/org/pkl/core/parser/Parser.java
+++ b/pkl-core/src/main/java/org/pkl/core/parser/Parser.java
@@ -29,7 +29,7 @@ import org.pkl.core.parser.antlr.PklParser;
 import org.pkl.core.parser.antlr.PklParser.*;
 import org.pkl.core.util.Nullable;

-public class Parser {
+public final class Parser {
  @TruffleBoundary
  public PklParser createParser(
      TokenStream stream, @Nullable List<LexParseException> errorCollector) {
--- a/pkl-core/src/main/java/org/pkl/core/project/CanonicalPackageUri.java
+++ b/pkl-core/src/main/java/org/pkl/core/project/CanonicalPackageUri.java
@@ -29,7 +29,7 @@ import org.pkl.core.util.ErrorMessages;
 * package://example.com/foo/bar@0}. Does not include a URI's userinfo, query params or fragment
 * segments.
 */
-public class CanonicalPackageUri {
+public final class CanonicalPackageUri {
  private final URI baseUri;
  private final int majorVersion;

--- a/pkl-core/src/main/java/org/pkl/core/project/DeclaredDependencies.java
+++ b/pkl-core/src/main/java/org/pkl/core/project/DeclaredDependencies.java
@@ -21,7 +21,7 @@ import org.pkl.core.packages.Dependency.RemoteDependency;
 import org.pkl.core.packages.PackageUri;
 import org.pkl.core.util.Nullable;

-public class DeclaredDependencies {
+public final class DeclaredDependencies {
  private final Map<String, RemoteDependency> remoteDependencies;
  private final Map<String, DeclaredDependencies> localDependencies;
  private final URI projectFileUri;
--- a/pkl-core/src/main/java/org/pkl/core/project/ProjectDependenciesResolver.java
+++ b/pkl-core/src/main/java/org/pkl/core/project/ProjectDependenciesResolver.java
@@ -43,7 +43,7 @@ import org.pkl.core.util.Nullable;
 *
 * <p>Resolved dependencies have URI `projectpackage` to indicate that they should be project-local.
 */
-public class ProjectDependenciesResolver {
+public final class ProjectDependenciesResolver {
  private final Project project;
  private final PackageResolver packageResolver;
  private final Writer logWriter;
--- a/pkl-core/src/main/java/org/pkl/core/project/ProjectDeps.java
+++ b/pkl-core/src/main/java/org/pkl/core/project/ProjectDeps.java
@@ -75,7 +75,7 @@ import org.pkl.core.util.json.JsonWriter;
 * </pre>
 * </code>
 */
-public class ProjectDeps {
+public final class ProjectDeps {
  private static final Set<Integer> supportedSchemaVersions = Set.of(1);

  private final EconomicMap<CanonicalPackageUri, Dependency> resolvedDependencies;
--- a/pkl-core/src/main/java/org/pkl/core/project/ProjectPackager.java
+++ b/pkl-core/src/main/java/org/pkl/core/project/ProjectPackager.java
@@ -78,7 +78,7 @@ import org.pkl.core.util.Pair;
 *   <li><em>thepackage@1.0.0.zip.sha256</em> - the SHA-256 checksum of the zip archive
 * </ul>
 */
-public class ProjectPackager {
+public final class ProjectPackager {
  /**
   * Modification time value for all zip entries in a package, to ensure that archives are
   * reproducible.
--- a/pkl-core/src/main/java/org/pkl/core/runtime/FileSystemManager.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/FileSystemManager.java
@@ -40,7 +40,9 @@ import org.pkl.core.util.EconomicMaps;
 *
 * <p>File systems are only closed when the last usage of it closes.
 */
-public class FileSystemManager {
+public final class FileSystemManager {
+  private FileSystemManager() {}
+
  private static final EconomicMap<URI, FileSystem> fileSystems = EconomicMaps.create();

  private static final Map<FileSystem, Integer> counts = new IdentityHashMap<>();
@@ -98,7 +100,7 @@ public class FileSystemManager {
    }
  }

-  private static class Handle extends FileSystem {
+  private static final class Handle extends FileSystem {

    final FileSystem delegate;

--- a/pkl-core/src/main/java/org/pkl/core/runtime/KeyLookupSuggestions.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/KeyLookupSuggestions.java
@@ -22,7 +22,9 @@ import org.pkl.core.ValueFormatter;
 import org.pkl.core.util.Nullable;
 import org.pkl.core.util.StringSimilarity;

-public class KeyLookupSuggestions {
+public final class KeyLookupSuggestions {
+  private KeyLookupSuggestions() {}
+
  private static final StringSimilarity STRING_SIMILARITY = new StringSimilarity();
  // 0.77 is just about low enough to consider two three-character
  // keys that differ in their first character similar
--- a/pkl-core/src/main/java/org/pkl/core/runtime/MemberLookupSuggestions.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/MemberLookupSuggestions.java
@@ -24,7 +24,7 @@ import org.pkl.core.util.EconomicMaps;
 import org.pkl.core.util.Nullable;
 import org.pkl.core.util.StringSimilarity;

-public class MemberLookupSuggestions {
+public final class MemberLookupSuggestions {
  private static final StringSimilarity STRING_SIMILARITY = new StringSimilarity();
  // 0.77 is just about low enough to consider two three-character
  // names that differ in their first character similar
--- a/pkl-core/src/main/java/org/pkl/core/runtime/ProjectModule.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/ProjectModule.java
@@ -17,7 +17,7 @@ package org.pkl.core.runtime;

 import static org.pkl.core.PClassInfo.pklProjectUri;

-public class ProjectModule extends StdLibModule {
+public final class ProjectModule extends StdLibModule {
  private static final VmTyped instance = VmUtils.createEmptyModule();

  static {
--- a/pkl-core/src/main/java/org/pkl/core/runtime/StackTraceGenerator.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/StackTraceGenerator.java
@@ -24,7 +24,7 @@ import org.pkl.core.StackFrame;
 import org.pkl.core.ast.MemberNode;
 import org.pkl.core.util.Nullable;

-class StackTraceGenerator {
+final class StackTraceGenerator {
  private final VmException exception;

  private final List<StackFrame> frames = new ArrayList<>();
--- a/pkl-core/src/main/java/org/pkl/core/runtime/StackTraceRenderer.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/StackTraceRenderer.java
@@ -21,7 +21,7 @@ import java.util.function.Function;
 import org.pkl.core.StackFrame;
 import org.pkl.core.util.Nullable;

-public class StackTraceRenderer {
+public final class StackTraceRenderer {
  private final Function<StackFrame, StackFrame> frameTransformer;

  public StackTraceRenderer(Function<StackFrame, StackFrame> frameTransformer) {
--- a/pkl-core/src/main/java/org/pkl/core/runtime/TestRunner.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/TestRunner.java
@@ -32,7 +32,7 @@ import org.pkl.core.util.MutableBoolean;
 import org.pkl.core.util.MutableReference;

 /** Runs test results examples and facts. */
-public class TestRunner {
+public final class TestRunner {
  private static final PklConverter converter = new PklConverter(VmMapping.empty());
  private final boolean overwrite;
  private final StackFrameTransformer stackFrameTransformer;
--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmExceptionBuilder.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmExceptionBuilder.java
@@ -47,7 +47,7 @@ import org.pkl.core.util.Nullable;
 *       preferable but isn't currently used. One problem with special formatting is that error
 *       output doesn't always go to a terminal and hence may be rendered verbatim.)
 */
-public class VmExceptionBuilder {
+public final class VmExceptionBuilder {

  private @Nullable Object receiver;

--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmExceptionRenderer.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmExceptionRenderer.java
@@ -24,7 +24,7 @@ import org.pkl.core.util.ErrorMessages;
 import org.pkl.core.util.Nullable;
 import org.pkl.core.util.StringBuilderWriter;

-public class VmExceptionRenderer {
+public final class VmExceptionRenderer {
  private final @Nullable StackTraceRenderer stackTraceRenderer;

  /**
--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmFileDetector.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmFileDetector.java
@@ -19,7 +19,7 @@ import java.nio.file.Path;
 import java.nio.file.spi.FileTypeDetector;
 import org.pkl.core.util.Nullable;

-public class VmFileDetector extends FileTypeDetector {
+public final class VmFileDetector extends FileTypeDetector {
  @Override
  public @Nullable String probeContentType(Path path) {
    var fileName = path.getFileName();
--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmStackOverflowException.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmStackOverflowException.java
@@ -17,7 +17,7 @@ package org.pkl.core.runtime;

 import java.util.List;

-public class VmStackOverflowException extends VmException {
+public final class VmStackOverflowException extends VmException {

  public VmStackOverflowException(StackOverflowError e) {
    super("stackOverflow", e, true, new Object[0], List.of(), null, null, null, null);
--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmValueRenderer.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmValueRenderer.java
@@ -28,7 +28,7 @@ import org.pkl.core.util.MutableBoolean;
 * <p>Currently prints fully qualified class name for outermost object (if rendered value is an
 * object) and omits class names otherwise.
 */
-public class VmValueRenderer {
+public final class VmValueRenderer {
  private final int lengthLimit;
  private final String leadingOrTrailingNewline;
  private final String interiorNewline;
--- a/pkl-core/src/main/java/org/pkl/core/service/ExecutorSpiImpl.java
+++ b/pkl-core/src/main/java/org/pkl/core/service/ExecutorSpiImpl.java
@@ -39,7 +39,7 @@ import org.pkl.executor.spi.v1.ExecutorSpiException;
 import org.pkl.executor.spi.v1.ExecutorSpiOptions;
 import org.pkl.executor.spi.v1.ExecutorSpiOptions2;

-public class ExecutorSpiImpl implements ExecutorSpi {
+public final class ExecutorSpiImpl implements ExecutorSpi {
  private static final int MAX_HTTP_CLIENTS = 3;

  // Don't create a new HTTP client for every executor request.
--- a/pkl-core/src/main/java/org/pkl/core/stdlib/PathConverterSupport.java
+++ b/pkl-core/src/main/java/org/pkl/core/stdlib/PathConverterSupport.java
@@ -17,7 +17,8 @@ package org.pkl.core.stdlib;

 import org.pkl.core.runtime.Identifier;

-public class PathConverterSupport {
+final class PathConverterSupport {
+  private PathConverterSupport() {}

  public static boolean pathMatches(Iterable<Object> pathSpec, Iterable<Object> path) {
    var pathIterator = path.iterator();
--- a/pkl-core/src/main/java/org/pkl/core/stdlib/json/ParserNodes.java
+++ b/pkl-core/src/main/java/org/pkl/core/stdlib/json/ParserNodes.java
@@ -32,7 +32,7 @@ import org.pkl.core.util.json.JsonHandler;
 import org.pkl.core.util.json.JsonParser;
 import org.pkl.core.util.json.ParseException;

-public class ParserNodes {
+public final class ParserNodes {
  private ParserNodes() {}

  public abstract static class parse extends ExternalMethod1Node {
--- a/pkl-core/src/main/java/org/pkl/core/stdlib/test/report/JUnitReport.java
+++ b/pkl-core/src/main/java/org/pkl/core/stdlib/test/report/JUnitReport.java
@@ -34,7 +34,7 @@ import org.pkl.core.stdlib.PklConverter;
 import org.pkl.core.stdlib.xml.RendererNodes.Renderer;
 import org.pkl.core.util.EconomicMaps;

-public class JUnitReport implements TestReport {
+public final class JUnitReport implements TestReport {

  @Override
  public void report(TestResults results, Writer writer) throws IOException {
--- a/pkl-core/src/main/java/org/pkl/core/stdlib/test/report/SimpleReport.java
+++ b/pkl-core/src/main/java/org/pkl/core/stdlib/test/report/SimpleReport.java
@@ -23,7 +23,7 @@ import org.pkl.core.runtime.TestResults.Failure;
 import org.pkl.core.runtime.TestResults.TestResult;
 import org.pkl.core.util.StringUtils;

-public class SimpleReport implements TestReport {
+public final class SimpleReport implements TestReport {

  @Override
  public void report(TestResults results, Writer writer) throws IOException {
--- a/pkl-core/src/main/java/org/pkl/core/util/ByteArrayUtils.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/ByteArrayUtils.java
@@ -19,7 +19,9 @@ import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import org.pkl.core.runtime.VmExceptionBuilder;

-public class ByteArrayUtils {
+public final class ByteArrayUtils {
+  private ByteArrayUtils() {}
+
  public static String md5(byte[] input) {
    return hash(input, "MD5");
  }
@@ -38,7 +40,7 @@ public class ByteArrayUtils {

  /**
   * Implemented directly instead of using JRE's `new BigInteger.toString(16)` so we can AOT-compile
-   * this and not need a truffle boundary.
+   * this and do not need a Truffle boundary.
   */
  public static String toHex(byte[] hash) {
    //    return new BigInteger(hash).toString(16);
--- a/pkl-core/src/main/java/org/pkl/core/util/CollectionUtils.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/CollectionUtils.java
@@ -19,7 +19,7 @@ import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;

-public class CollectionUtils {
+public final class CollectionUtils {
  private static final float LOAD_FACTOR = 0.75f;

  private CollectionUtils() {}
--- a/pkl-core/src/main/java/org/pkl/core/util/ErrorMessages.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/ErrorMessages.java
@@ -20,7 +20,9 @@ import java.util.Locale;
 import java.util.ResourceBundle;
 import java.util.stream.*;

-public class ErrorMessages {
+public final class ErrorMessages {
+  private ErrorMessages() {}
+
  public static String create(String messageName, Object... args) {
    var locale = Locale.getDefault();
    String errorMessage =
--- a/pkl-core/src/main/java/org/pkl/core/util/GlobResolver.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/GlobResolver.java
@@ -33,14 +33,16 @@ import org.pkl.core.module.ModuleKey;
 import org.pkl.core.module.PathElement;
 import org.pkl.core.runtime.ReaderBase;

-public class GlobResolver {
-  public static class InvalidGlobPatternException extends Exception {
+public final class GlobResolver {
+  private GlobResolver() {}
+
+  public static final class InvalidGlobPatternException extends Exception {
    public InvalidGlobPatternException(String message) {
      super(message);
    }
  }

-  public static class ResolvedGlobElement {
+  public static final class ResolvedGlobElement {
    private final String path;

    private final URI uri;
--- a/pkl-core/src/main/java/org/pkl/core/util/StringBuilderWriter.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/StringBuilderWriter.java
@@ -17,7 +17,7 @@ package org.pkl.core.util;

 import java.io.Writer;

-public class StringBuilderWriter extends Writer {
+public final class StringBuilderWriter extends Writer {
  private final StringBuilder builder;

  public StringBuilderWriter(StringBuilder builder) {
--- a/pkl-core/src/main/java/org/pkl/core/util/StringSimilarity.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/StringSimilarity.java
@@ -29,7 +29,7 @@ import javax.annotation.concurrent.Immutable;
 * @author Thibault Debatty
 */
@Immutable
-public class StringSimilarity {
+public final class StringSimilarity {
  private static final double DEFAULT_THRESHOLD = 0.7;
  private static final int THREE = 3;
  private static final double JW_COEF = 0.1;
--- a/pkl-core/src/main/java/org/pkl/core/util/json/Json.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/json/Json.java
@@ -68,7 +68,7 @@ import org.pkl.core.util.Nullable;
 * </table>
 */
@SuppressWarnings("unused")
-public class Json {
+public final class Json {
  @FunctionalInterface
  public interface Mapper<R> {
    R apply(Object arg) throws Exception;
--- a/pkl-core/src/main/java/org/pkl/core/util/json/JsonWriter.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/json/JsonWriter.java
@@ -127,11 +127,11 @@ import org.pkl.core.util.Nullable;
 * @since 1.6
 */
@SuppressWarnings({"unused", "UnusedReturnValue"})
-public class JsonWriter implements Closeable, Flushable {
+public final class JsonWriter implements Closeable, Flushable {
  /** An array with no elements requires no separators or newlines before it is closed. */
  static final int EMPTY_ARRAY = 1;

-  /** A array with at least one value requires a comma and newline before the next element. */
+  /** An array with at least one value requires a comma and newline before the next element. */
  static final int NONEMPTY_ARRAY = 2;

  /** An object with no name/value pairs requires no separators or newlines before it is closed. */
@@ -200,7 +200,7 @@ public class JsonWriter implements Closeable, Flushable {
   *
   * @param indent a string containing only whitespace.
   */
-  public final void setIndent(String indent) {
+  public void setIndent(String indent) {
    if (indent.isEmpty()) {
      this.indent = null;
      this.separator = ":";
@@ -221,7 +221,7 @@ public class JsonWriter implements Closeable, Flushable {
   *   <li>Numbers may be {@link Double#isNaN() NaNs} or {@link Double#isInfinite() infinities}.
   * </ul>
   */
-  public final void setLenient(boolean lenient) {
+  public void setLenient(boolean lenient) {
    this.lenient = lenient;
  }

@@ -236,7 +236,7 @@ public class JsonWriter implements Closeable, Flushable {
   * them to the stream. Without this setting, your XML/HTML encoder should replace these characters
   * with the corresponding escape sequences.
   */
-  public final void setHtmlSafe(boolean htmlSafe) {
+  public void setHtmlSafe(boolean htmlSafe) {
    this.htmlSafe = htmlSafe;
    this.escaper = new JsonEscaper(htmlSafe);
  }
@@ -244,7 +244,7 @@ public class JsonWriter implements Closeable, Flushable {
  /**
   * Returns true if this writer writes JSON that's safe for inclusion in HTML and XML documents.
   */
-  public final boolean isHtmlSafe() {
+  public boolean isHtmlSafe() {
    return htmlSafe;
  }

@@ -252,7 +252,7 @@ public class JsonWriter implements Closeable, Flushable {
   * Sets whether object members are serialized when their value is null. This has no impact on
   * array elements. The default is true.
   */
-  public final void setSerializeNulls(boolean serializeNulls) {
+  public void setSerializeNulls(boolean serializeNulls) {
    this.serializeNulls = serializeNulls;
  }

@@ -260,7 +260,7 @@ public class JsonWriter implements Closeable, Flushable {
   * Returns true if object members are serialized when their value is null. This has no impact on
   * array elements. The default is true.
   */
-  public final boolean getSerializeNulls() {
+  public boolean getSerializeNulls() {
    return serializeNulls;
  }

--- a/pkl-core/src/main/java/org/pkl/core/util/properties/PropertiesUtils.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/properties/PropertiesUtils.java
@@ -17,7 +17,7 @@ package org.pkl.core.util.properties;

 import java.io.BufferedWriter;

-public class PropertiesUtils {
+public final class PropertiesUtils {

  // Bitmap of characters that need escaping ('\t', '\n', '\f', '\r', ' ', '!', '#', ':', '=', '\\')
  // in four 32-bit segments.
--- a/pkl-core/src/main/java/org/pkl/core/util/yaml/Yaml11Emitter.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/yaml/Yaml11Emitter.java
@@ -18,7 +18,7 @@ package org.pkl.core.util.yaml;
 import org.pkl.core.util.IoUtils;

@SuppressWarnings("DuplicatedCode")
-public class Yaml11Emitter extends YamlEmitter {
+public final class Yaml11Emitter extends YamlEmitter {
  public Yaml11Emitter(StringBuilder builder, String indent) {
    super(builder, indent);
  }
--- a/pkl-core/src/main/java/org/pkl/core/util/yaml/Yaml12Emitter.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/yaml/Yaml12Emitter.java
@@ -18,7 +18,7 @@ package org.pkl.core.util.yaml;
 import org.pkl.core.util.IoUtils;

@SuppressWarnings("DuplicatedCode")
-public class Yaml12Emitter extends YamlEmitter {
+public final class Yaml12Emitter extends YamlEmitter {
  public Yaml12Emitter(StringBuilder builder, String indent) {
    super(builder, indent);
  }