diff --git a/c/native.c b/c/native.c
index 1d0f22c..7ac847a 100644
--- a/c/native.c
+++ b/c/native.c
@@ -10,6 +10,7 @@
 #include "native/object.h"
 #include "native/printstream.h"
 #include "native/runtime.h"
+#include "native/system.h"
 
 typedef void (* native_func_t)(struct vm * vm, uint32_t * args);
 
@@ -126,15 +127,9 @@ const static struct native_method native_method[] = {
   {
     .class_name = "java/lang/Object",
     .method_name = "_getClass",
-    .method_descriptor = "()Ljava/lang/Class;",
+    .method_descriptor = "(Ljava/lang/Object;)Ljava/lang/Class;",
     .func = native_java_lang_object_getclass_1,
   },
-  {
-    .class_name = "java/lang/Object",
-    .method_name = "_hashCode",
-    .method_descriptor = "()I",
-    .func = native_java_lang_object_hashcode_1,
-  },
   {
     .class_name = "java/lang/Runtime",
     .method_name = "_freeMemory",
@@ -153,6 +148,12 @@ const static struct native_method native_method[] = {
     .method_descriptor = "()I",
     .func = native_java_lang_runtime_totalmemory_0,
   },
+  {
+    .class_name = "java/lang/System",
+    .method_name = "_hashCode",
+    .method_descriptor = "(Ljava/lang/Object;)I",
+    .func = native_java_lang_system_hashcode_1,
+  },
 };
 
 struct hash_table_entry * native_init_hash_table(int * hash_table_length)
diff --git a/c/native/object.c b/c/native/object.c
index 1475f66..8e7c3d6 100644
--- a/c/native/object.c
+++ b/c/native/object.c
@@ -1,5 +1,4 @@
 #include "object.h"
-#include "printf.h"
 #include "vm_instance.h"
 
 void native_java_lang_object_getclass_1(struct vm * vm, uint32_t * args)
@@ -15,9 +14,3 @@ void native_java_lang_object_getclass_1(struct vm * vm, uint32_t * args)
 
   operand_stack_push_ref(vm->current_frame, class_objectref);
 }
-
-void native_java_lang_object_hashcode_1(struct vm * vm, uint32_t * args)
-{
-  struct objectref * objectref = (struct objectref *)args[0];
-  operand_stack_push_u32(vm->current_frame, (uint32_t)objectref); // objectref as integer
-}
diff --git a/c/native/object.h b/c/native/object.h
index fb7e369..b9740a7 100644
--- a/c/native/object.h
+++ b/c/native/object.h
@@ -5,5 +5,3 @@
 #include "frame.h"
 
 void native_java_lang_object_getclass_1(struct vm * vm, uint32_t * args);
-
-void native_java_lang_object_hashcode_1(struct vm * vm, uint32_t * args);
diff --git a/c/native/system.c b/c/native/system.c
new file mode 100644
index 0000000..ab573b9
--- /dev/null
+++ b/c/native/system.c
@@ -0,0 +1,7 @@
+#include "system.h"
+
+void native_java_lang_system_hashcode_1(struct vm * vm, uint32_t * args)
+{
+  struct objectref * objectref = (struct objectref *)args[0];
+  operand_stack_push_u32(vm->current_frame, (uint32_t)objectref); // objectref as integer
+}
diff --git a/c/native/system.h b/c/native/system.h
new file mode 100644
index 0000000..b624b8e
--- /dev/null
+++ b/c/native/system.h
@@ -0,0 +1,7 @@
+#pragma once
+
+#include <stdint.h>
+
+#include "frame.h"
+
+void native_java_lang_system_hashcode_1(struct vm * vm, uint32_t * args);
diff --git a/classes/java/lang/Object.java b/classes/java/lang/Object.java
index 7f37027..e9f6db2 100644
--- a/classes/java/lang/Object.java
+++ b/classes/java/lang/Object.java
@@ -12,16 +12,14 @@ public class Object {
         return this == obj;
     }
 
-    private final native Class<?> _getClass();
+    private final native static Class<?> _getClass(Object o);
 
     public final Class<?> getClass() {
-        return _getClass();
+        return _getClass(this);
     }
 
-    private native int _hashCode();
-
     public int hashCode() {
-        return _hashCode();
+        return System.identityHashCode(this);
     }
 
     public String toString() {
diff --git a/classes/java/lang/System.java b/classes/java/lang/System.java
index c7e2da8..63b809d 100644
--- a/classes/java/lang/System.java
+++ b/classes/java/lang/System.java
@@ -3,11 +3,23 @@ package java.lang;
 import java.io.PrintStream;
 
 public final class System {
-    public static PrintStream out = null;
+    public static PrintStream err;
+    public static PrintStream out;
 
     private System() {
     }
     static {
         out = new PrintStream();
+        err = new PrintStream();
+    }
+
+    public static void gc() {
+        Runtime.getRuntime().gc();
+    }
+
+    private final native static int _hashCode(Object x);
+
+    public static int identityHashCode(Object x) {
+        return _hashCode(x);
     }
 }
diff --git a/java.mk b/java.mk
index 51b4fa4..b7ebe53 100644
--- a/java.mk
+++ b/java.mk
@@ -28,6 +28,7 @@ OBJ = \
 	c/native/object.o \
 	c/native/printstream.o \
 	c/native/runtime.o \
+	c/native/system.o \
 	c/parse.o \
 	c/parse_type.o \
 	c/printf.o \