performance test

build.gradle

@@ -51,8 +51,8 @@ pitest {
 spotbugs {
     toolVersion = '4.9.8'
     excludeFilter = file('spotbugs-exclude.xml')
-    effort = "max"
-    reportLevel = "low"
+    effort = com.github.spotbugs.snom.Effort.valueOf("MAX")
+    reportLevel = com.github.spotbugs.snom.Confidence.valueOf("LOW")
     reportsDir = layout.buildDirectory.dir('spotbugs')
 }
 
@@ -84,7 +84,7 @@ tasks.spotbugsTest {
 }
 
 pmd {
-    toolVersion = '7.0.0'
+    toolVersion = '7.21.0'
     ruleSetFiles = files('pmd-rules.xml')
     ruleSets = [] // Disable default rulesets, use custom file only
     consoleOutput = true
@@ -128,7 +128,7 @@ tasks.checkstyleTest {
 
 dependencies {
     implementation 'tools.jackson.core:jackson-databind:3.0.4'
-    implementation 'tools.jackson.module:jackson-module-afterburner:3.0.4'
+    implementation 'tools.jackson.module:jackson-module-blackbird:3.0.4'
     compileOnly 'com.github.spotbugs:spotbugs-annotations:4.9.8'
     testImplementation platform('org.junit:junit-bom:6.0.2')
     testImplementation 'org.junit.jupiter:junit-jupiter'
@@ -140,12 +140,26 @@ dependencies {
     testAnnotationProcessor 'org.openjdk.jmh:jmh-generator-annprocess:1.37'
 }
 
+// Check if running in CI or coverage is explicitly requested
+boolean isCi = System.getenv('CI') == 'true'
+boolean withCoverage = project.hasProperty('withCoverage') || isCi
+
 test {
     useJUnitPlatform()
-    finalizedBy jacocoTestReport // report is always generated after tests run
+    // Only run jacoco coverage in CI or when explicitly requested
+    if (withCoverage) {
+        finalizedBy jacocoTestReport
+        jacoco {
+            enabled = true
+        }
+    } else {
+        // Completely disable jacoco for local development
+        jacoco {
+            enabled = false
+        }
+    }
 }
 
-
 jacocoTestReport {
     dependsOn test
     reports {
@@ -156,6 +170,8 @@ jacocoTestReport {
 }
 
 jacocoTestCoverageVerification {
+    // Only enforce coverage thresholds in CI
+    onlyIf { isCi }
     violationRules {
         rule {
             enabled = true
@@ -174,6 +190,11 @@ jacocoTestCoverageVerification {
         }
     }
 }
+
+// Only add coverage verification to check task in CI
+if (isCi) {
+    check.dependsOn jacocoTestCoverageVerification
+}
 check.dependsOn jacocoTestReport
 check.dependsOn spotbugsMain
 check.dependsOn pmdMain
@@ -203,7 +224,7 @@ tasks.register('jmh', JavaExec) {
     group = 'verification'
     description = 'Run JMH benchmarks'
     classpath = configurations.testRuntimeClasspath + sourceSets.test.runtimeClasspath
-    mainClass = 'dev.toonformat.jtoon.JToonBenchmark'
+    mainClass = findProperty('benchmarkClass') ?: 'dev.toonformat.jtoon.JToonBenchmark'
     workingDir = projectDir
     doFirst {
         file('build/jmh-results').mkdirs()

pmd-rules-test.xml

@@ -11,13 +11,15 @@
     <!-- Best Practices -->
     <rule ref="category/java/bestpractices.xml">
         <exclude name="GuardLogStatement" />
-        <exclude name="JUnitAssertionsShouldIncludeMessage" />
-        <exclude name="JUnitTestContainsTooManyAsserts" />
-        <exclude name="JUnitTestsShouldIncludeAssert" />
         <exclude name="JUnitUseExpected" />
         <exclude name="LiteralsFirstInComparisons" />
         <exclude name="JUnit5TestShouldBePackagePrivate" />
         <exclude name="LooseCoupling" />
+        <exclude name="RelianceOnDefaultCharset" />
+        <exclude name="UnnecessaryVarargsArrayCreation" />
+        <exclude name="UnitTestAssertionsShouldIncludeMessage" />
+        <exclude name="UnitTestContainsTooManyAsserts" />
+        <exclude name="UnitTestShouldIncludeAssert" />
     </rule>
 
     <!-- Code Style -->
@@ -28,6 +30,7 @@
         <exclude name="ConfusingTernary" />
         <exclude name="ControlStatementBraces" />
         <exclude name="FieldNamingConventions" />
+        <exclude name="LambdaCanBeMethodReference" />
         <exclude name="LinguisticNaming" />
         <exclude name="LocalVariableCouldBeFinal" />
         <exclude name="LongVariable" />
@@ -70,6 +73,7 @@
         <exclude name="LoosePackageCoupling" />
         <exclude name="NPathComplexity" />
         <exclude name="NcssCount" />
+        <exclude name="PublicMemberInNonPublicType" />
         <exclude name="SignatureDeclareThrowsException" />
         <exclude name="SimplifiedTernary" />
         <exclude name="SimplifyBooleanReturns" />
@@ -81,6 +85,7 @@
 
     <!-- Error Prone -->
     <rule ref="category/java/errorprone.xml">
+        <exclude name="AvoidCatchingGenericException" />
         <exclude name="AvoidDuplicateLiterals" />
         <exclude name="AvoidFieldNameMatchingMethodName" />
         <exclude name="AvoidLiteralsInIfCondition" />
@@ -102,6 +107,8 @@
         <exclude name="MissingSerialVersionUID" />
         <exclude name="NullAssignment" />
         <exclude name="ProperCloneImplementation" />
+        <exclude name="ReplaceJavaUtilCalendar" />
+        <exclude name="ReplaceJavaUtilDate" />
         <exclude name="ReturnFromFinallyBlock" />
         <exclude name="SimpleDateFormatNeedsLocale" />
         <exclude name="SingletonClassReturningNewInstance" />
@@ -120,6 +127,7 @@
         <exclude name="InefficientEmptyStringCheck" />
         <exclude name="InsufficientStringBufferDeclaration" />
         <exclude name="OptimizableToArrayCall" />
+        <exclude name="TooFewBranchesForSwitch" />
         <exclude name="UseArrayListInsteadOfVector" />
         <exclude name="UseStringBufferForStringAppends" />
     </rule>

pmd-rules.xml

@@ -11,9 +11,8 @@
     <!-- Best Practices -->
     <rule ref="category/java/bestpractices.xml">
         <exclude name="GuardLogStatement" />
-        <exclude name="JUnitAssertionsShouldIncludeMessage" />
-        <exclude name="JUnitTestContainsTooManyAsserts" />
-        <exclude name="JUnitTestsShouldIncludeAssert" />
+        <exclude name="ForLoopCanBeForeach" />
+        <exclude name="UnusedPrivateMethod" />
         <exclude name="JUnitUseExpected" />
     </rule>
 
@@ -40,13 +39,13 @@
     <!-- Design -->
     <rule ref="category/java/design.xml">
         <exclude name="AbstractClassWithoutAnyMethod" />
-        <exclude name="AvoidCatchingGenericException" />
         <exclude name="AvoidDeeplyNestedIfStmts" />
         <exclude name="CognitiveComplexity" />
         <exclude name="CollapsibleIfStatements" />
         <exclude name="CyclomaticComplexity" />
         <exclude name="DataClass" />
         <exclude name="ExcessiveImports" />
+        <exclude name="ExcessiveParameterList" />
         <exclude name="ExcessivePublicCount" />
         <exclude name="GodClass" />
         <exclude name="ImmutableField" />
@@ -64,6 +63,7 @@
 
     <!-- Error Prone -->
     <rule ref="category/java/errorprone.xml">
+        <exclude name="AvoidCatchingGenericException" />
         <exclude name="AvoidLiteralsInIfCondition" />
         <exclude name="AvoidMultipleUnaryOperators" />
         <exclude name="CheckSkipResult" />

spotbugs-exclude.xml

@@ -11,6 +11,17 @@
         <Class name="~.*JToonBenchmark.*" />
     </Match>
 
+    <!-- Exclude JMH generated classes -->
+    <Match>
+        <Class name="~.*jmh_generated.*" />
+    </Match>
+
+    <!-- Exclude NM_CONFUSING for JMH benchmark methods -->
+    <Match>
+        <Class name="~.*Benchmark.*" />
+        <Bug pattern="NM_CONFUSING" />
+    </Match>
+
     <!-- Exclude generated classes -->
     <Match>
         <Class name="~.*\.generated\..*" />

src/main/java/dev/toonformat/jtoon/JToon.java

@@ -4,6 +4,7 @@
 import dev.toonformat.jtoon.encoder.ValueEncoder;
 import dev.toonformat.jtoon.normalizer.JsonNormalizer;
 import tools.jackson.databind.JsonNode;
+import java.util.Objects;
 
 /**
  * Main entry point for encoding and decoding TOON (Token-Oriented Object Notation) format.
@@ -41,8 +42,10 @@ public static String encode(final Object input) {
      * @param input   The object to encode (can be null)
      * @param options Encoding options (indent, delimiter, length marker)
      * @return The JToon-formatted string
+     * @throws NullPointerException if options is null
      */
     public static String encode(final Object input, final EncodeOptions options) {
+        Objects.requireNonNull(options, "EncodeOptions cannot be null");
         final JsonNode normalizedValue = JsonNormalizer.normalize(input);
         return ValueEncoder.encodeValue(normalizedValue, options);
     }
@@ -68,17 +71,17 @@ public static String encodeJson(final String json) {
      * Encodes a plain JSON string to TOON format using custom options.
      *
      * <p>
-     * Parsing is delegated to
-     * {@link JsonNormalizer#parse(String)}
-     * to maintain separation of concerns.
+     * Parses the JSON string to a tree structure, then encodes to TOON format.
      * </p>
      *
      * @param json    The JSON string to encode (must be valid JSON)
      * @param options Encoding options (indent, delimiter, length marker)
      * @return The TOON-formatted string
      * @throws IllegalArgumentException if the input is not valid JSON
+     * @throws NullPointerException if options is null
      */
     public static String encodeJson(final String json, final EncodeOptions options) {
+        Objects.requireNonNull(options, "EncodeOptions cannot be null");
         final JsonNode parsed = JsonNormalizer.parse(json);
         return ValueEncoder.encodeValue(parsed, options);
     }
@@ -113,8 +116,10 @@ public static Object decode(final String toon) {
      * @return Parsed object (Map, List, primitive, or null)
      * @throws IllegalArgumentException if strict mode is enabled and input is
      *                                  invalid
+     * @throws NullPointerException if options is null
      */
     public static Object decode(final String toon, final DecodeOptions options) {
+        Objects.requireNonNull(options, "DecodeOptions cannot be null");
         return ValueDecoder.decode(toon, options);
     }
 
@@ -150,8 +155,10 @@ public static String decodeToJson(final String toon) {
      * @return JSON string representation
      * @throws IllegalArgumentException if strict mode is enabled and input is
      *                                  invalid
+     * @throws NullPointerException if options is null
      */
     public static String decodeToJson(final String toon, final DecodeOptions options) {
+        Objects.requireNonNull(options, "DecodeOptions cannot be null");
         return ValueDecoder.decodeToJson(toon, options);
     }
 }

src/main/java/dev/toonformat/jtoon/encoder/ArrayEncoder.java

@@ -4,9 +4,7 @@
 import tools.jackson.databind.JsonNode;
 import tools.jackson.databind.node.ArrayNode;
 import tools.jackson.databind.node.ObjectNode;
-import java.util.ArrayList;
 import java.util.List;
-import java.util.stream.StreamSupport;
 import static dev.toonformat.jtoon.util.Constants.LIST_ITEM_PREFIX;
 import static dev.toonformat.jtoon.util.Constants.SPACE;
 
@@ -39,26 +37,47 @@ public static void encodeArray(final String key, final ArrayNode value,
             return;
         }
 
-        // Primitive array
-        if (isArrayOfPrimitives(value)) {
+        final int size = value.size();
+        boolean allPrimitives = true;
+        boolean allArrays = true;
+        boolean allObjects = true;
+
+        for (int i = 0; i < size; i++) {
+            final JsonNode item = value.get(i);
+            if (!item.isValueNode()) {
+                allPrimitives = false;
+            }
+            if (!item.isArray()) {
+                allArrays = false;
+            }
+            if (!item.isObject()) {
+                allObjects = false;
+            }
+            if (!allPrimitives && !allArrays && !allObjects) {
+                break;
+            }
+        }
+
+        if (allPrimitives) {
             encodeInlinePrimitiveArray(key, value, writer, depth, options);
             return;
         }
 
-        // Array of arrays (all primitives)
-        if (isArrayOfArrays(value)) {
-            final boolean allPrimitiveArrays = StreamSupport.stream(value.spliterator(), false)
-                    .filter(JsonNode::isArray)
-                    .allMatch(ArrayEncoder::isArrayOfPrimitives);
-
+        if (allArrays) {
+            boolean allPrimitiveArrays = true;
+            for (int i = 0; i < size; i++) {
+                if (!isArrayOfPrimitives(value.get(i))) {
+                    allPrimitiveArrays = false;
+                    break;
+                }
+            }
             if (allPrimitiveArrays) {
                 encodeArrayOfArraysAsListItems(key, value, writer, depth, options);
                 return;
             }
         }
 
-        // Array of objects
-        if (isArrayOfObjects(value)) {
+        if (allObjects) {
             final List<String> header = TabularArrayEncoder.detectTabularHeader(value);
             if (!header.isEmpty()) {
                 TabularArrayEncoder.encodeArrayOfObjectsAsTabular(key, value, header, writer, depth, options);
@@ -68,7 +87,6 @@ public static void encodeArray(final String key, final ArrayNode value,
             return;
         }
 
-        // Mixed array: fallback to expanded format
         encodeMixedArrayAsListItems(key, value, writer, depth, options);
     }
 
@@ -147,17 +165,25 @@ private static void encodeInlinePrimitiveArray(final String prefix, final ArrayN
      */
     public static String formatInlineArray(final ArrayNode values, final String delimiter,
             final String prefix, final boolean lengthMarker) {
-        final List<JsonNode> valueList = new ArrayList<>();
-        values.forEach(valueList::add);
-
         final String header = PrimitiveEncoder.formatHeader(values.size(), prefix, null, delimiter, lengthMarker);
-        final String joinedValue = PrimitiveEncoder.joinEncodedValues(valueList, delimiter);
 
-        // Only add space if there are values
+        // Early return for empty arrays
         if (values.isEmpty()) {
             return header;
         }
-        return header + SPACE + joinedValue;
+
+        // Build joined values directly without intermediate collection
+        final StringBuilder joinedValues = new StringBuilder(128);
+        boolean first = true;
+        for (final JsonNode value : values) {
+            if (!first) {
+                joinedValues.append(delimiter);
+            }
+            first = false;
+            joinedValues.append(PrimitiveEncoder.encodePrimitive(value, delimiter));
+        }
+
+        return header + SPACE + joinedValues;
     }
 
     /**

src/main/java/dev/toonformat/jtoon/encoder/Flatten.java

@@ -42,7 +42,7 @@ public record FoldResult(String foldedKey,
      * @param tail      the tail node (if any)
      * @param leafValue the leaf JsonValue
      */
-    private record ChainResult(List<String> segments, JsonNode tail, JsonNode leafValue) {
+    record ChainResult(List<String> segments, JsonNode tail, JsonNode leafValue) {
     }
 
     /**
@@ -136,7 +136,7 @@ public static FoldResult tryFoldKeyChain(final String key,
      * @param maxDepth   maximum number of allowed segments
      * @return a {@link ChainResult} containing segments, tail, and leafValue
      */
-    private static ChainResult collectSingleKeyChain(final String startKey,
+    static ChainResult collectSingleKeyChain(final String startKey,
                                                      final JsonNode startValue,
                                                      final int maxDepth) {
         // normalize absolute key to its local segment