diff --git a/src/heap.rs b/src/heap.rs
index 4674255..e5464c5 100644
--- a/src/heap.rs
+++ b/src/heap.rs
@@ -20,7 +20,25 @@ pub enum ObjectRef {
     StringArray(Vec<String>),
     ObjectArray(Type, Vec<Arc<UnsafeCell<ObjectRef>>>),
     Object(Box<Object>),
-    Class(Arc<RefCell<Class>>)
+    Class(Arc<RefCell<Class>>),
+}
+
+impl ObjectRef {
+    pub fn get_array_length(&self) -> usize {
+        match self {
+            ByteArray(d) => d.len(),
+            ShortArray(d) => d.len(),
+            IntArray(d) => d.len(),
+            LongArray(d) => d.len(),
+            FloatArray(d) => d.len(),
+            DoubleArray(d) => d.len(),
+            BooleanArray(d) => d.len(),
+            CharArray(d) => d.len(),
+            StringArray(d) => d.len(),
+            ObjectArray(_, d) => d.len(),
+            _ => unreachable!("not an array")
+        }
+    }
 }
 
 fn into_vec_i8(v: Vec<u8>) -> Vec<i8> {
diff --git a/src/opcodes.rs b/src/opcodes.rs
index 99b29c5..cbac78f 100644
--- a/src/opcodes.rs
+++ b/src/opcodes.rs
@@ -286,7 +286,7 @@ pub const NEW: u8 = 187;
 // (0xbb) Create new object
 pub const ANEWARRAY: u8 = 189;
 // (0xbd)
-pub const _ARRAYLENGTH: u8 = 190;
+pub const ARRAYLENGTH: u8 = 190;
 // (0xbe)
 pub const _ATHROW: u8 = 191;
 // (0xbf)
@@ -440,7 +440,7 @@ pub const OPCODES:Lazy<Vec<&str>> = Lazy::new(|| {
     opcodes[INVOKESTATIC  as usize] = "INVOKESTATIC" ;
     opcodes[NEW  as usize] = "NEW" ;
     opcodes[ANEWARRAY  as usize] = "ANEWARRAY" ;
-    opcodes[_ARRAYLENGTH  as usize] = "_ARRAYLENGTH" ;
+    opcodes[ARRAYLENGTH  as usize] = "ARRAYLENGTH" ;
     opcodes[_ATHROW  as usize] = "_ATHROW" ;
     opcodes[_CHECKCAST  as usize] = "_CHECKCAST" ;
     opcodes[MONITORENTER  as usize] = "MONITORENTER" ;
diff --git a/src/vm.rs b/src/vm.rs
index d3c1f65..1ba4cae 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -671,6 +671,15 @@ impl Vm {
                             panic!();
                         }
                     },
+                    ARRAYLENGTH => {
+                        let val = self.current_frame().pop()?;
+                        unsafe {
+                            if let Ref(val) = &*val.get() {
+                                let o = &*val.get();
+                                self.current_frame().push(I32(o.get_array_length() as i32));
+                            }
+                        }
+                    }
                     MONITORENTER => {
                         self.current_frame().pop()?;
                     } //TODO implement
@@ -734,10 +743,10 @@ impl Vm {
         if let I32(index) = &*value.get() {
             let index = *index as usize;
             let arrayref = self.current_frame().pop()?;
-            if let Value::Null = &*arrayref.get() {
+            if let Null = &*arrayref.get() {
                 return Err(anyhow!("NullpointerException"));
             }
-            if let Value::Ref(objectref) = &*arrayref.get() {
+            if let Ref(objectref) = &*arrayref.get() {
                 match &*objectref.get() {
                     ObjectRef::ByteArray(array) => {
                         self.current_frame().push(I32(array[index] as i32));
@@ -766,7 +775,7 @@ impl Vm {
                     ObjectRef::ObjectArray(_arraytype, data) => {
                         self.current_frame().push(Ref(data[index].clone()));
                     }
-                    ObjectRef::StringArray(array) =>{
+                    ObjectRef::StringArray(array) => {
                         self.current_frame().push(Utf8(array[index].to_owned()));
                     }
                     ObjectRef::Class(_) => {