diff --git a/Dummy.class b/Dummy.class
index 17b5c76..2c18fc4 100644
Binary files a/Dummy.class and b/Dummy.class differ
diff --git a/Dummy.java b/Dummy.java
index 0c9c2f9..6b17104 100644
--- a/Dummy.java
+++ b/Dummy.java
@@ -1,22 +1,6 @@
-package dummy;
-
 public class Dummy {
 
-    private final static String constant = "meh";
-    private final int integer = 57;
-
-    private final String name;
-
-    public Dummy(String name) {
-        this.name = name;
+    public static int get(){
+        return 42;
     }
-
-    public String getName() {
-        return name;
-    }
-
-    public void print(){
-        System.out.println(name);
-    }
-
 }
diff --git a/src/lib.rs b/src/lib.rs
index 12eb869..e3eeec6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,8 @@
 pub mod types;
 mod io;
+pub mod opcodes;
 
+use std::collections::HashMap;
 use std::rc::Rc;
 use crate::io::{read_f32, read_f64, read_i32, read_i64, read_u16, read_u32};
 use crate::types::{AttributeType, Class, MethodCode, Exception, Field, Method};
@@ -38,18 +40,19 @@ pub fn get_class(bytecode: Vec<u8>) -> Option<Class> {
 
     let methods_count = read_u16(&bytecode, index);
     index += 2;
-    let mut methods = vec![];
+    let mut methods = HashMap::new();
     for _ in 0..methods_count {
-        methods.push(read_method(constant_pool.clone(), &mut index, &bytecode));
+        let m = read_method(constant_pool.clone(), &mut index, &bytecode);
+        methods.insert(m.name(), m);
     }
 
     let attributes_count = read_u16(&bytecode, index);
     index += 2;
-    let mut attributes = vec![];
+    let mut attributes = HashMap::new();
     for _ in 0..attributes_count {
         let some = read_attribute(constant_pool.clone(), &bytecode, &mut index);
         if let Some(att) = some {
-            attributes.push(att);
+            attributes.insert(att.0, att.1);
         } else {
             panic!(); // bug/not-implemented
         }
@@ -154,10 +157,10 @@ fn read_field(constant_pool: Rc<Vec<CpEntry>>, index: &mut usize, bytecode: &[u8
     let descriptor_index = read_u16(bytecode, *index + 4) as usize;
     let attributes_count = read_u16(bytecode, *index + 6);
     *index += 8;
-    let mut attributes = vec![];
+    let mut attributes = HashMap::new();
     for _ in 0..attributes_count {
         if let Some(att) = read_attribute(constant_pool.clone(), bytecode, index) {
-            attributes.push(att);
+            attributes.insert(att.0, att.1);
         } else {
             panic!(); // bug/not-implemented
         }
@@ -178,10 +181,10 @@ fn read_method(constant_pool: Rc<Vec<CpEntry>>, index: &mut usize, bytecode: &[u
     let attributes_count = read_u16(bytecode, *index + 6);
     *index += 8;
 
-    let mut attributes = vec![];
+    let mut attributes = HashMap::new();
     for _ in 0..attributes_count {
         if let Some(att) = read_attribute(constant_pool.clone(), bytecode, index) {
-            attributes.push(att);
+            attributes.insert(att.0, att.1);
         }
     }
 
@@ -194,7 +197,7 @@ fn read_method(constant_pool: Rc<Vec<CpEntry>>, index: &mut usize, bytecode: &[u
     )
 }
 
-fn read_attribute(constant_pool: Rc<Vec<CpEntry>>, bytecode: &[u8], index: &mut usize) -> Option<AttributeType> {
+fn read_attribute(constant_pool: Rc<Vec<CpEntry>>, bytecode: &[u8], index: &mut usize) -> Option<(String, AttributeType)> {
     let attribute_name_index = read_u16(bytecode, *index) as usize;
     *index += 2;
     let attribute_length = read_u32(bytecode, *index) as usize;
@@ -208,7 +211,7 @@ fn read_attribute(constant_pool: Rc<Vec<CpEntry>>, bytecode: &[u8], index: &mut
         return match s.as_str() {
             "ConstantValue" => {
                 assert_eq!(info.len(), 2);
-                Some(AttributeType::ConstantValue(read_u16(&info, 0)))
+                Some(("ConstantValue".into(), AttributeType::ConstantValue(read_u16(&info, 0))))
             }
             "Code" => {
                 let max_stack = read_u16(&info, 0);
@@ -225,15 +228,15 @@ fn read_attribute(constant_pool: Rc<Vec<CpEntry>>, bytecode: &[u8], index: &mut
                 }
                 let attribute_count = read_u16(&info, code_index);
                 code_index += 2;
-                let mut code_attributes = vec![];
+                let mut code_attributes = HashMap::new();
                 for _ in 0..attribute_count {
                     if let Some(att) = read_attribute(constant_pool.clone(), &info, &mut code_index) {
-                        code_attributes.push(att);
+                        code_attributes.insert(att.0, att.1);
                     }
                 }
-                Some(AttributeType::Code(MethodCode::new(max_stack, max_locals, code, exception_table, code_attributes)))
+                Some(("Code".into(), AttributeType::Code(MethodCode::new(max_stack, max_locals, code, exception_table, code_attributes))))
             }
-            "SourceFile" => Some(AttributeType::SourceFile),
+            "SourceFile" => Some(("SourceFile".into(), AttributeType::SourceFile)),
             _ => None
         };
     }
diff --git a/src/main.rs b/src/main.rs
index 113026a..37a303f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,8 +4,10 @@ use std::io::Read;
 fn main() {
     let bytecode = read_class_file("./Dummy.class");
     if let Some(class) = classfile_reader::get_class(bytecode){
-        println!("{:?}", class);
+        let ret = class.execute("public static get()I");
+        println!("{:?}", ret);
     }
+
 }
 
 fn read_class_file(name: &str) -> Vec<u8> {
diff --git a/src/opcodes.rs b/src/opcodes.rs
new file mode 100644
index 0000000..1b332aa
--- /dev/null
+++ b/src/opcodes.rs
@@ -0,0 +1,97 @@
+pub const aconst_null: u8 = 1; // (0x01)
+
+pub const fconst_0: u8 = 11; // (0xb) Push float 0
+pub const fconst_1: u8 = 12; // (0xc) Push float 1
+pub const fconst_2: u8 = 13; // (0xd) Push float 2
+pub const dconst_0:u8 = 14; // (0xe) push double 0
+pub const dconst_1:u8 = 15; // (0xf) push double 1
+pub const bipush:u8 = 16; // (0x10) Push byte
+
+pub const ldc: u8 = 18; // (0x12) Push item from run-time pub constant pool
+pub const fload:u8 = 23; // (0x17) Load float from local variable
+pub const dload:u8 = 24; // (0x18) load double from local variable
+pub const aload:u8 = 25; //0x19
+
+pub const fload_0:u8 = 34; // (0x22) Load float 0 from local variable
+pub const fload_1:u8 = 35; // (0x23) Load float 1 from local variable
+pub const fload_2:u8 = 36; // (0x24) Load float 2 from local variable
+pub const fload_3:u8 = 37; // (0x25) Load float 3 from local variable
+pub const dload_0:u8 = 38; //  (0x26) Load double 0 from local variable
+pub const dload_1:u8 = 39; //  (0x27) Load double 1 from local variable
+pub const dload_2:u8 = 40; //  (0x28) Load double 2 from local variable
+pub const dload_3:u8 = 41; // (0x29) Load double 3 from local variable
+pub const aload_0:u8 = 42;// (0x2a)
+pub const aload_1:u8 = 43;// (0x2a)
+pub const aload_2:u8 = 44;// (0x2b)
+pub const aload_3:u8 = 45;// (0x2c)
+
+pub const faload: u8 = 48; // (0x30) Load float from array
+pub const daload:u8 = 49; // (0x31) load double from array
+pub const aaload: u8 = 50; // (0x3d)
+pub const baload: u8 = 51; //(0x33)
+pub const caload: u8 = 52; // (0x34)
+
+pub const fstore: u8 = 56; // (0x38) Store float into local variable
+pub const dstore: u8 = 57; // (0x39) store double in local variable
+pub const astore:u8 = 58; // (0x3a)
+
+pub const dstore_0: u8 = 71; // (0x47) store double 0 in local variable
+pub const dstore_1: u8 = 72; // (0x48) store double 1 in local variable
+pub const dstore_2: u8 = 73; // (0x49) store double 2 in local variable
+pub const dstore_3: u8 = 74; // (0x4a) store double 3 in local variable
+pub const astore_0: u8 = 75; // (0x4b)
+pub const astore_1: u8 = 76; // (0x4c)
+pub const astore_2: u8 = 77; // (0x4d)
+pub const astore_3: u8 = 78; // (0x4e)
+pub const fastore: u8 = 81; // (0x51) Store into float array
+pub const dastore:u8 = 82; //(0x52) store into double array
+pub const aastore: u8 = 83; // (0x53)
+
+pub const bastore:u8 = 84; // (0x54)
+
+pub const castore:u8 = 85; // (0x55)
+pub const dup:u8 = 89; // (0x59) duplicate the top operand stack value
+pub const dup_x1: u8 = 90; // (0x5a) Duplicate the top operand stack value and insert two values down
+pub const dup_x2: u8 = 91; // (0x5b) Duplicate the top operand stack value and insert two or three values down
+pub const dup2: u8 = 92; // (0x5c) Duplicate the top one or two operand stack values
+pub const dup2_x1: u8 = 93; //(0x5d) Duplicate the top one or two operand stack values and insert two or three values down
+pub const dup2_x2:u8 = 94; // (0x5e) Duplicate the top one or two operand stack values and insert two, three, or four values down
+pub const fadd: u8 = 98; // (0x62) Add float
+pub const dadd: u8 = 99; // (0x63) add double
+
+pub const dsub:u8 = 103; // (0x67) subtract double
+pub const fmul: u8 = 106; // (0x6a) Multiply float
+pub const dmul: u8 = 107; // (0x6b) Multiply double
+
+pub const fdiv: u8 = 110; // (0x6e) Divide float
+pub const ddiv:u8 = 111; // (0x6f) divide double
+pub const frem: u8 = 114; // (0x72) Remainder float
+pub const drem: u8 = 115; // (0x73) remainder double
+pub const fneg: u8 = 118; // (0x76) Negate float
+pub const dneg: u8 = 119; // (0x77) Negate double
+pub const f2i: u8 = 139; // (0x8b) Convert float to int
+pub const f2l: u8 = 140; // (0x8c) Convert float to long
+pub const f2d: u8 = 141; // (0x8d) Convert float to double
+pub const d2i:u8 = 142; // (0x8e) double to int
+pub const d2l:u8 = 143; // (0x8f) double to long
+pub const d2f: u8 = 144; // (0x90) double to float
+pub const fcmpl:u8 = 149; // (0x95) Compare float (less than)
+pub const fcmpg: u8 = 150; // (0x96) Compare float (greater than)
+pub const dcmpl:u8 = 151; // (0x97) compare double (less than)
+pub const dcmpg:u8 = 152; // (0x98) compare double (greater than)
+
+pub const ireturn: u8 = 172; // (0xac) ireturn
+pub const freturn: u8 = 174; // (0xae) Return float from method
+pub const dreturn: u8 = 175; // (0xaf) Return double from method
+pub const areturn: u8 = 176; //(0xb0) return reference
+pub const return_v: u8 = 177; // (0xb1) Return void from method (actually 'return' but that's a keyword)
+pub const invokevirtual: u8 = 182; // (0xb6) Invoke instance method; dispatch based on class
+
+pub const getstatic: u8 = 178; // (0xb2) Get static field from class
+pub const anewarray: u8 = 189; // (0xbd)
+
+pub const arraylength: u8 = 190; // (0xbe)
+
+pub const athrow: u8 = 191; // (0xbf)
+
+pub const checkcast: u8 = 192; // (0xc0)
diff --git a/src/types.rs b/src/types.rs
index dd1999a..ab7daff 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -1,5 +1,6 @@
+use std::collections::HashMap;
 use std::rc::Rc;
-use crate::CpEntry;
+use crate::{CpEntry, opcodes};
 
 #[derive(Debug)]
 //TODO create factory function
@@ -12,14 +13,19 @@ pub struct Class {
     pub super_class: u16,
     pub interfaces: Vec<u16>,
     pub fields: Vec<Field>,
-    pub methods: Vec<Method>,
-    pub attributes: Vec<AttributeType>,
+    pub methods: HashMap<String, Method>,
+    pub attributes: HashMap<String, AttributeType>,
 }
 
 impl Class {
     pub fn get_version(&self) -> (u16, u16) {
         (self.major_version, self.minor_version)
     }
+
+    pub fn execute(&self, method_name: &str) -> Value {
+        let m = self.methods.get(method_name).unwrap();
+        m.execute().unwrap() //TODO remove unwrap
+    }
 }
 
 pub struct Method {
@@ -27,7 +33,7 @@ pub struct Method {
     access_flags: u16,
     name_index: usize,
     descriptor_index: usize,
-    attributes: Vec<AttributeType>,
+    attributes: HashMap<String, AttributeType>,
 }
 
 impl fmt::Debug for Method {
@@ -42,7 +48,7 @@ impl Method {
                access_flags: u16,
                name_index: usize,
                descriptor_index: usize,
-               attributes: Vec<AttributeType>, ) -> Self {
+               attributes: HashMap<String, AttributeType>, ) -> Self {
         Method { constant_pool, access_flags, name_index, descriptor_index, attributes }
     }
 
@@ -59,16 +65,29 @@ impl Method {
         full_name
     }
 
-    // pub fn get_code(&self) {
-    //     for att in &self.attributes {
-    //         if let CpEntry::Utf8(_, str) = &self.constant_pool[&att.attribute_name_index - 1] {
-    //             println!("{}", str);
-    //             if str == "Code" {
-    //                 println!("{:?}", att.info);
-    //             }
-    //         }
-    //     }
-    // }
+    pub fn execute(&self) -> Option<Value> {
+        if let AttributeType::Code(code) = self.attributes.get("Code").unwrap() {
+            let mut stack = Stack::new();
+            let mut pc: usize = 0;
+            while pc < code.opcodes.len() {
+                let opcode = &code.opcodes[pc];
+                match opcode {
+                    &opcodes::bipush => {
+                        pc += 1;
+                        let c = code.opcodes[pc] as i32;
+                        stack.push(Value::I32(c));
+                    },
+                    &opcodes::ireturn => {
+                        return stack.pop();
+                    },
+                    //TODO implement all opcodes
+                    _ => {}
+                }
+                pc += 1;
+            }
+        }
+        None // TODO error situation
+    }
 }
 
 pub struct Field {
@@ -76,10 +95,11 @@ pub struct Field {
     access_flags: u16,
     name_index: usize,
     descriptor_index: usize,
-    attributes: Vec<AttributeType>,
+    attributes: HashMap<String, AttributeType>,
 }
 
 use std::fmt;
+use std::hash::Hash;
 use crate::io::read_u16;
 
 impl fmt::Debug for Field {
@@ -94,7 +114,7 @@ impl Field {
                access_flags: u16,
                name_index: usize,
                descriptor_index: usize,
-               attributes: Vec<AttributeType>, ) -> Self {
+               attributes: HashMap<String, AttributeType>, ) -> Self {
         Field { constant_pool, access_flags, name_index, descriptor_index, attributes: attributes }
     }
 
@@ -193,16 +213,42 @@ impl Exception {
 pub struct MethodCode {
     max_stack: u16,
     max_locals: u16,
-    code: Vec<u8>,
+    opcodes: Vec<u8>,
     exception_table: Vec<Exception>,
-    code_attributes: Vec<AttributeType>,
+    code_attributes: HashMap<String, AttributeType>,
 }
 
 impl MethodCode {
     pub(crate) fn new(max_stack: u16, max_locals: u16,
                       code: Vec<u8>,
                       exception_table: Vec<Exception>,
-                      code_attributes: Vec<AttributeType>) -> Self {
-        Self { max_stack, max_locals, code, exception_table, code_attributes }
+                      code_attributes: HashMap<String, AttributeType>) -> Self {
+        Self { max_stack, max_locals, opcodes: code, exception_table, code_attributes }
     }
+}
+
+struct Stack {
+    data: Vec<Value>,
+}
+
+impl Stack {
+    fn new() -> Self {
+        Self {
+            data: vec![]
+        }
+    }
+
+    fn push(&mut self, val: Value) {
+        self.data.push(val);
+    }
+
+    fn pop(&mut self) -> Option<Value> {
+        self.data.pop()
+    }
+}
+
+#[derive(Debug)]
+pub enum Value {
+    Void,
+    I32(i32),
 }
\ No newline at end of file