diff --git a/src/Exceptions/ConverterException.php b/src/Exceptions/ConverterException.php
deleted file mode 100644
index e11c9456..00000000
--- a/src/Exceptions/ConverterException.php
+++ /dev/null
@@ -1,6 +0,0 @@
-<?php
-namespace PHPJava\Exceptions;
-
-class ConverterException extends \Exception
-{
-}
diff --git a/src/Exceptions/NormalizerException.php b/src/Exceptions/NormalizerException.php
new file mode 100644
index 00000000..0766ab50
--- /dev/null
+++ b/src/Exceptions/NormalizerException.php
@@ -0,0 +1,6 @@
+<?php
+namespace PHPJava\Exceptions;
+
+class NormalizerException extends \Exception
+{
+}
diff --git a/src/Kernel/Mnemonics/_invokevirtual.php b/src/Kernel/Mnemonics/_invokevirtual.php
index 6ed384d6..cb65c6be 100644
--- a/src/Kernel/Mnemonics/_invokevirtual.php
+++ b/src/Kernel/Mnemonics/_invokevirtual.php
@@ -10,7 +10,7 @@
 use PHPJava\Utilities\AttributionResolver;
 use PHPJava\Utilities\BinaryTool;
 use PHPJava\Utilities\ClassResolver;
-use PHPJava\Utilities\Converter;
+use PHPJava\Utilities\Normalizer;
 use PHPJava\Utilities\Formatter;
 use PHPJava\Utilities\TypeResolver;
 
@@ -37,7 +37,7 @@ public function execute(): void
                 $arguments[$i] = $this->popFromOperandStack();
             }
 
-            $arguments = Converter::normalizeArguments(
+            $arguments = Normalizer::normalizeValues(
                 $arguments,
                 $signature['arguments']
             );
diff --git a/src/Kernel/Types/_Array/Collection.php b/src/Kernel/Types/_Array/Collection.php
index 645f5fb6..e16bcf5c 100644
--- a/src/Kernel/Types/_Array/Collection.php
+++ b/src/Kernel/Types/_Array/Collection.php
@@ -6,9 +6,10 @@
 use PHPJava\Utilities\Extractor;
 use PHPJava\Utilities\TypeResolver;
 
-class Collection implements \ArrayAccess
+class Collection implements \ArrayAccess, \Countable, \IteratorAggregate
 {
     private $data;
+    private $position = 0;
 
     public function __construct(array &$data, string $type = null)
     {
@@ -54,4 +55,14 @@ public function offsetSet($offset, $value)
     {
         $this->data[$offset] = $value;
     }
+
+    public function count()
+    {
+        return count($this->data);
+    }
+
+    public function getIterator()
+    {
+        return new \ArrayIterator($this->data);
+    }
 }
diff --git a/src/Utilities/Converter.php b/src/Utilities/Converter.php
deleted file mode 100644
index 6d29e0e1..00000000
--- a/src/Utilities/Converter.php
+++ /dev/null
@@ -1,48 +0,0 @@
-<?php
-namespace PHPJava\Utilities;
-
-use PHPJava\Exceptions\ConverterException;
-use PHPJava\Kernel\Types\_Array\Collection;
-use PHPJava\Kernel\Types\Type;
-
-class Converter
-{
-
-    /**
-     * @param array $arguments
-     * @param array $acceptedArguments
-     * @return array
-     * @throws ConverterException
-     */
-    public static function normalizeArguments(array $arguments, array $acceptedArguments): array
-    {
-        if (count($arguments) !== count($acceptedArguments)) {
-            throw new ConverterException('Does not match arguments.');
-        }
-
-        foreach ($arguments as $key => &$argument) {
-            /**
-             * @var Type|Collection $argument
-             */
-            if ($argument instanceof Collection) {
-                // TODO: convert an array contents.
-                continue;
-            }
-            $realType = $acceptedArguments[$key] ?? null;
-            if ($realType === null) {
-                throw new ConverterException('Broken arguments parser.');
-            }
-            if ($realType['type'] === 'class') {
-                // TODO: implements up-cast and down-cast
-                continue;
-            }
-            $initiateClass = TypeResolver::TYPES_MAP[$realType['type']];
-            if ($argument instanceof $initiateClass) {
-                continue;
-            }
-            $argument = new $initiateClass(Extractor::realValue($argument));
-        }
-
-        return $arguments;
-    }
-}
diff --git a/src/Utilities/Normalizer.php b/src/Utilities/Normalizer.php
new file mode 100644
index 00000000..f769ac61
--- /dev/null
+++ b/src/Utilities/Normalizer.php
@@ -0,0 +1,57 @@
+<?php
+namespace PHPJava\Utilities;
+
+use PHPJava\Exceptions\NormalizerException;
+use PHPJava\Kernel\Types\_Array\Collection;
+use PHPJava\Kernel\Types\Type;
+
+class Normalizer
+{
+
+    /**
+     * @param array|Collection $values
+     * @param array $normalizeTypes
+     * @return array|Collection
+     * @throws NormalizerException
+     */
+    public static function normalizeValues($values, array $normalizeTypes)
+    {
+        if (count($values) !== count($normalizeTypes)) {
+            throw new NormalizerException('Does not match arguments.');
+        }
+
+        foreach ($values as $key => &$value) {
+            $realType = $normalizeTypes[$key] ?? null;
+            if ($realType === null) {
+                throw new NormalizerException('Broken arguments parser.');
+            }
+            /**
+             * @var Type|Collection $value
+             */
+            if ($value instanceof Collection) {
+                $value = static::normalizeValues(
+                    $value,
+                    array_fill(
+                        0,
+                        count($value),
+                        $realType
+                    )
+                );
+                continue;
+            }
+            if ($realType['type'] === 'class') {
+                // TODO: implements up-cast and down-cast
+                continue;
+            }
+            $initiateClass = TypeResolver::TYPES_MAP[$realType['type']];
+            if ($value instanceof $initiateClass) {
+                continue;
+            }
+            $value = new $initiateClass(
+                Extractor::realValue($value)
+            );
+        }
+
+        return $values;
+    }
+}