Comply with explicit API mode to library code.

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/CollectionBuilder.kt

@@ -22,26 +22,26 @@ package org.apache.fury.serializer.kotlin
 /**
  * Collection builder interface adapts an iterable to allow incremental build by the fury protocol.
  */
-interface CollectionBuilder<E, T : Iterable<E>> {
-  fun add(element: E): Boolean
+public interface CollectionBuilder<E, T : Iterable<E>> {
+  public fun add(element: E): Boolean
 
-  fun result(): T
+  public fun result(): T
 }
 
 /** Abstract builder for [kotlin.collections.List] interface. */
-abstract class AbstractListBuilder<E, T : List<E>> :
+public abstract class AbstractListBuilder<E, T : List<E>> :
   CollectionBuilder<E, T>, AdaptedCollection<E>() {
   protected open val builder: MutableList<E> = mutableListOf()
   override val size: Int
     get() = builder.size
 
-  override fun add(element: E) = builder.add(element)
+  override fun add(element: E): Boolean = builder.add(element)
 
   override fun iterator(): MutableIterator<E> = builder.iterator()
 }
 
 /** Builder for [kotlin.collections.ArrayDeque]. */
-class ArrayDequeBuilder<E>(override val builder: ArrayDeque<E>) :
+public class ArrayDequeBuilder<E>(override val builder: ArrayDeque<E>) :
   AbstractListBuilder<E, ArrayDeque<E>>() {
   override fun result(): ArrayDeque<E> = builder
 }

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/CollectionSerializer.kt

@@ -25,7 +25,7 @@ import org.apache.fury.serializer.collection.AbstractCollectionSerializer
 
 /** Serializer for kotlin collections. */
 @Suppress("UNCHECKED_CAST")
-abstract class AbstractKotlinCollectionSerializer<E, T : Iterable<E>>(fury: Fury, cls: Class<T>) :
+public abstract class AbstractKotlinCollectionSerializer<E, T : Iterable<E>>(fury: Fury, cls: Class<T>) :
   AbstractCollectionSerializer<T>(fury, cls) {
   abstract override fun onCollectionWrite(buffer: MemoryBuffer, value: T): Collection<E>
 
@@ -43,7 +43,7 @@ abstract class AbstractKotlinCollectionSerializer<E, T : Iterable<E>>(fury: Fury
 }
 
 /** Serializer for [[kotlin.collections.ArrayDeque]]. */
-class KotlinArrayDequeSerializer<E>(
+public class KotlinArrayDequeSerializer<E>(
   fury: Fury,
   cls: Class<ArrayDeque<E>>,
 ) : AbstractKotlinCollectionSerializer<E, ArrayDeque<E>>(fury, cls) {
@@ -60,7 +60,7 @@ class KotlinArrayDequeSerializer<E>(
   }
 }
 
-typealias AdaptedCollection<E> = java.util.AbstractCollection<E>
+public typealias AdaptedCollection<E> = java.util.AbstractCollection<E>
 
 /** An adapter which wraps a kotlin iterable into a [[java.util.Collection]]. */
 private class IterableAdapter<E>(coll: Iterable<E>) : AdaptedCollection<E>() {

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/DurationSerializer.kt

@@ -33,10 +33,10 @@ import org.apache.fury.memory.MemoryBuffer
 import org.apache.fury.serializer.ImmutableSerializer
 import org.apache.fury.serializer.Serializer
 
-class DurationSerializer(fury: Fury, needToWriteRef: Boolean) :
+public class DurationSerializer(fury: Fury, needToWriteRef: Boolean) :
   ImmutableSerializer<Duration>(fury, Duration::class.java, needToWriteRef) {
 
-  constructor(
+  public constructor(
     fury: Fury,
   ) : this(fury, fury.config.isTimeRefIgnored)
 

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/KotlinToJavaClass.kt

@@ -21,7 +21,7 @@ package org.apache.fury.serializer.kotlin
 
 import kotlin.random.Random
 
-object KotlinToJavaClass {
+internal object KotlinToJavaClass {
   // Collections
   val ArrayDequeClass = ArrayDeque::class.java
   val EmptyListClass = emptyList<Any>().javaClass

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/UnsignedArraySerializers.kt

@@ -26,7 +26,7 @@ import org.apache.fury.memory.MemoryBuffer
 import org.apache.fury.serializer.Serializer
 import org.apache.fury.type.Type
 
-abstract class AbstractDelegatingArraySerializer<T, T_Delegate>(
+public abstract class AbstractDelegatingArraySerializer<T, T_Delegate>(
   fury: Fury,
   cls: Class<T>,
   private val delegateClass: Class<T_Delegate>
@@ -35,9 +35,9 @@ abstract class AbstractDelegatingArraySerializer<T, T_Delegate>(
   // Lazily initialize the delegatingSerializer here to avoid lookup cost.
   private val delegatingSerializer by lazy { fury.classResolver.getSerializer(delegateClass) }
 
-  abstract fun toDelegateClass(value: T): T_Delegate
+  protected abstract fun toDelegateClass(value: T): T_Delegate
 
-  abstract fun fromDelegateClass(value: T_Delegate): T
+  protected abstract fun fromDelegateClass(value: T_Delegate): T
 
   override fun getXtypeId(): Short {
     return (-Type.LIST.id).toShort()
@@ -61,62 +61,62 @@ abstract class AbstractDelegatingArraySerializer<T, T_Delegate>(
   }
 }
 
-class UByteArraySerializer(
+public class UByteArraySerializer(
   fury: Fury,
 ) :
   AbstractDelegatingArraySerializer<UByteArray, ByteArray>(
     fury,
     UByteArray::class.java,
     ByteArray::class.java
   ) {
-  override fun toDelegateClass(value: UByteArray) = value.toByteArray()
+  override fun toDelegateClass(value: UByteArray): ByteArray = value.toByteArray()
 
-  override fun fromDelegateClass(value: ByteArray) = value.toUByteArray()
+  override fun fromDelegateClass(value: ByteArray): UByteArray = value.toUByteArray()
 
   override fun copy(value: UByteArray): UByteArray = value.copyOf()
 }
 
-class UShortArraySerializer(
+public class UShortArraySerializer(
   fury: Fury,
 ) :
   AbstractDelegatingArraySerializer<UShortArray, ShortArray>(
     fury,
     UShortArray::class.java,
     ShortArray::class.java
   ) {
-  override fun toDelegateClass(value: UShortArray) = value.toShortArray()
+  override fun toDelegateClass(value: UShortArray): ShortArray = value.toShortArray()
 
-  override fun fromDelegateClass(value: ShortArray) = value.toUShortArray()
+  override fun fromDelegateClass(value: ShortArray): UShortArray = value.toUShortArray()
 
-  override fun copy(value: UShortArray) = value.copyOf()
+  override fun copy(value: UShortArray): UShortArray = value.copyOf()
 }
 
-class UIntArraySerializer(
+public class UIntArraySerializer(
   fury: Fury,
 ) :
   AbstractDelegatingArraySerializer<UIntArray, IntArray>(
     fury,
     UIntArray::class.java,
     IntArray::class.java
   ) {
-  override fun toDelegateClass(value: UIntArray) = value.toIntArray()
+  override fun toDelegateClass(value: UIntArray): IntArray = value.toIntArray()
 
-  override fun fromDelegateClass(value: IntArray) = value.toUIntArray()
+  override fun fromDelegateClass(value: IntArray): UIntArray = value.toUIntArray()
 
-  override fun copy(value: UIntArray) = value.copyOf()
+  override fun copy(value: UIntArray): UIntArray = value.copyOf()
 }
 
-class ULongArraySerializer(
+public class ULongArraySerializer(
   fury: Fury,
 ) :
   AbstractDelegatingArraySerializer<ULongArray, LongArray>(
     fury,
     ULongArray::class.java,
     LongArray::class.java
   ) {
-  override fun toDelegateClass(value: ULongArray) = value.toLongArray()
+  override fun toDelegateClass(value: ULongArray): LongArray = value.toLongArray()
 
-  override fun fromDelegateClass(value: LongArray) = value.toULongArray()
+  override fun fromDelegateClass(value: LongArray): ULongArray = value.toULongArray()
 
-  override fun copy(value: ULongArray) = value.copyOf()
+  override fun copy(value: ULongArray): ULongArray = value.copyOf()
 }

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/UnsignedSerializer.kt

@@ -29,7 +29,7 @@ import org.apache.fury.type.Type
  *
  * UByte is mapped to Type.UINT8
  */
-class UByteSerializer(
+public class UByteSerializer(
   fury: Fury,
 ) :
   Serializers.CrossLanguageCompatibleSerializer<UByte>(
@@ -54,7 +54,7 @@ class UByteSerializer(
  *
  * UShort is mapped to Type.UINT16.
  */
-class UShortSerializer(
+public class UShortSerializer(
   fury: Fury,
 ) :
   Serializers.CrossLanguageCompatibleSerializer<UShort>(
@@ -78,7 +78,7 @@ class UShortSerializer(
  *
  * UInt is mapped to Type.UINT32.
  */
-class UIntSerializer(
+public class UIntSerializer(
   fury: Fury,
 ) :
   Serializers.CrossLanguageCompatibleSerializer<UInt>(
@@ -103,7 +103,7 @@ class UIntSerializer(
  *
  * ULong is mapped to Type.UINT64.
  */
-class ULongSerializer(
+public class ULongSerializer(
   fury: Fury,
 ) :
   Serializers.CrossLanguageCompatibleSerializer<ULong>(

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/UuidSerializer.kt

@@ -26,7 +26,7 @@ import org.apache.fury.memory.MemoryBuffer
 import org.apache.fury.serializer.ImmutableSerializer
 
 @OptIn(ExperimentalUuidApi::class)
-class UuidSerializer(fury: Fury) : ImmutableSerializer<Uuid>(fury, Uuid::class.java) {
+public class UuidSerializer(fury: Fury) : ImmutableSerializer<Uuid>(fury, Uuid::class.java) {
   override fun write(buffer: MemoryBuffer, value: Uuid) {
     value.toLongs { msb, lsb ->
       buffer.writeInt64(msb)