diff --git a/src/main/java/ASTGenerator.java b/src/main/java/ASTGenerator.java
index 0d9570f..8629671 100644
--- a/src/main/java/ASTGenerator.java
+++ b/src/main/java/ASTGenerator.java
@@ -1,5 +1,4 @@
 import abstractSyntaxTree.Class.FieldDecl;
-import abstractSyntaxTree.Class.IClass;
 import abstractSyntaxTree.Class.MethodDecl;
 import abstractSyntaxTree.Class.RefType;
 import abstractSyntaxTree.Expression.BinaryExpression;
@@ -11,7 +10,6 @@ import abstractSyntaxTree.Statement.*;
 import gen.DecafBaseVisitor;
 import gen.DecafParser;
 
-import java.beans.Expression;
 import java.util.ArrayList;
 import java.util.List;
 
diff --git a/src/main/java/Compiler.java b/src/main/java/Compiler.java
index 28e65da..8d3fd73 100644
--- a/src/main/java/Compiler.java
+++ b/src/main/java/Compiler.java
@@ -1,5 +1,14 @@
 import abstractSyntaxTree.Class.RefType;
+import abstractSyntaxTree.Datatype.BoolDatatype;
+import abstractSyntaxTree.Datatype.IntDatatype;
+import abstractSyntaxTree.Expression.InstVarExpression;
+import abstractSyntaxTree.Expression.LocalVarIdentifier;
+import abstractSyntaxTree.Expression.UnaryExpression;
 import abstractSyntaxTree.Program;
+import abstractSyntaxTree.Statement.IStatement;
+import abstractSyntaxTree.Statement.LocalVarDecl;
+import abstractSyntaxTree.Statement.ReturnStatement;
+import abstractSyntaxTree.StatementExpression.AssignStatementExpression;
 import gen.DecafLexer;
 import gen.DecafParser;
 import org.antlr.v4.runtime.CharStream;
@@ -81,6 +90,15 @@ public class Compiler {
 //            System.out.println(refType.name);
 //        }
 
+        abstractSyntaxTree.classes.get(1).methodDecls.get(0).codeBlock.returnType = "int";
+        List<IStatement> statementsList = abstractSyntaxTree.classes.get(1).methodDecls.get(0).codeBlock.statements;
+        statementsList.add(new LocalVarDecl("int", "localInt"));
+        statementsList.add(new LocalVarDecl("bool", "localBool"));
+        statementsList.add(new LocalVarDecl("char", "localChar"));
+        statementsList.add(new AssignStatementExpression("=", new LocalVarIdentifier("localInt"), new UnaryExpression("", new IntDatatype())));
+        //statementsList.add(new AssignStatementExpression("=", new InstVarExpression(abstractSyntaxTree.classes.get(1)), new UnaryExpression("instVarBool", new BoolDatatype())));
+
+        abstractSyntaxTree.classes.get(1).methodDecls.get(0).codeBlock.statements.add(new ReturnStatement(new UnaryExpression("", new IntDatatype())));
         abstractSyntaxTree.typeCheck();
 
         abstractSyntaxTree.codeGen();
diff --git a/src/main/java/Input.java b/src/main/java/Input.java
index 034e89e..ea16d77 100644
--- a/src/main/java/Input.java
+++ b/src/main/java/Input.java
@@ -5,7 +5,9 @@ class Example {
 
 }
 class Example2 {
-    int i;
-    boolean j;
+    boolean instVarBool;
+    void m(int i){
+        return;
+    }
 
 }
diff --git a/src/main/java/TestClass.java b/src/main/java/TestClass.java
new file mode 100644
index 0000000..39c1383
--- /dev/null
+++ b/src/main/java/TestClass.java
@@ -0,0 +1,6 @@
+public class TestClass {
+    public static void main(String[] args){
+        new Example();
+        new Example2();
+    }
+}
diff --git a/src/main/java/TypeCheck/TypeCheckHelper.java b/src/main/java/TypeCheck/TypeCheckHelper.java
index 5d487d8..b62cd43 100644
--- a/src/main/java/TypeCheck/TypeCheckHelper.java
+++ b/src/main/java/TypeCheck/TypeCheckHelper.java
@@ -12,8 +12,9 @@ public class TypeCheckHelper {
         if(type1Primitiv && type2Primitiv){
             if(Objects.equals(type1, type2)){
                 result = type1;
+            }else{
+                throw new Exception("no upper bound");
             }
-            throw new Exception("no upper bound");
         }else if(type1Primitiv || type2Primitiv){
             throw new Exception("no upper bound");
         }else{
diff --git a/src/main/java/abstractSyntaxTree/Class/FieldDecl.java b/src/main/java/abstractSyntaxTree/Class/FieldDecl.java
index 0e2e0c1..54c0951 100644
--- a/src/main/java/abstractSyntaxTree/Class/FieldDecl.java
+++ b/src/main/java/abstractSyntaxTree/Class/FieldDecl.java
@@ -13,7 +13,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 
-public class FieldDecl extends AbstractType implements IClass, Node {
+public class FieldDecl extends AbstractType implements Node {
 
     public String type; // from parser
     public String identifier; // from parser
@@ -39,7 +39,6 @@ public class FieldDecl extends AbstractType implements IClass, Node {
         return null;
     }
 
-    @Override
     public void codeGen(ClassWriter cw) {
         //TODO: Do we have fields with initial values?
         FieldVisitor fv = cw.visitField(Opcodes.ACC_PUBLIC, identifier, getFieldDescriptor(), null, null);
diff --git a/src/main/java/abstractSyntaxTree/Class/IClass.java b/src/main/java/abstractSyntaxTree/Class/IClass.java
deleted file mode 100644
index e71c991..0000000
--- a/src/main/java/abstractSyntaxTree/Class/IClass.java
+++ /dev/null
@@ -1,16 +0,0 @@
-package abstractSyntaxTree.Class;
-
-import TypeCheck.TypeCheckResult;
-import org.objectweb.asm.ClassWriter;
-import org.objectweb.asm.TypeReference;
-
-import java.util.HashMap;
-import java.util.List;
-
-public interface IClass {
-    // visit method for code generation
-
-
-    void codeGen(ClassWriter cw) throws Exception;
-
-}
diff --git a/src/main/java/abstractSyntaxTree/Class/MethodDecl.java b/src/main/java/abstractSyntaxTree/Class/MethodDecl.java
index a1fc503..9348e38 100644
--- a/src/main/java/abstractSyntaxTree/Class/MethodDecl.java
+++ b/src/main/java/abstractSyntaxTree/Class/MethodDecl.java
@@ -14,7 +14,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Stack;
 
-public class MethodDecl implements IClass, Node {
+public class MethodDecl implements Node {
 
     //Class Name
     public String classThatContainsMethod;
@@ -36,14 +36,15 @@ public class MethodDecl implements IClass, Node {
         this.localVars = new HashMap<>();
     }
 
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
         // jede methode als block statement aufrufen und jede neue locale varibale in localvars schreiben
 
-        codeBlock.typeCheck(methodContext, typeContext);
-        return null;
+        TypeCheckResult result = new TypeCheckResult();
+        codeBlock.typeCheck(methodContext, typeContext, localVars);
+        result.type = codeBlock.returnType;
+        return result;
     }
 
-    @Override
     public void codeGen(ClassWriter cw) throws Exception {
 
         localVars.put("this", classThatContainsMethod);
diff --git a/src/main/java/abstractSyntaxTree/Class/RefType.java b/src/main/java/abstractSyntaxTree/Class/RefType.java
index 7702d36..83ef3a2 100644
--- a/src/main/java/abstractSyntaxTree/Class/RefType.java
+++ b/src/main/java/abstractSyntaxTree/Class/RefType.java
@@ -3,6 +3,7 @@ package abstractSyntaxTree.Class;
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Node;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Opcodes;
 
@@ -10,7 +11,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 
-public class RefType extends AbstractType implements IClass, Node {
+public class RefType extends AbstractType implements Node {
 
     //Class Name
     public String name;
@@ -29,7 +30,7 @@ public class RefType extends AbstractType implements IClass, Node {
         this.hasMain = hasMain;
     }
 
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext,
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext,
                                      HashMap<String, HashMap<String, String>> typeContext) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
 
@@ -72,7 +73,7 @@ public class RefType extends AbstractType implements IClass, Node {
 
     // Method for code generation which iterates over all the field declarations
     // and method declarations and calls their CodeGen methods
-    @Override
+
     public void codeGen(ClassWriter cw) throws Exception {
 
         cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, name, null,
diff --git a/src/main/java/abstractSyntaxTree/Expression/VarRefExpression.java b/src/main/java/abstractSyntaxTree/Expression/LocalVarIdentifier.java
similarity index 52%
rename from src/main/java/abstractSyntaxTree/Expression/VarRefExpression.java
rename to src/main/java/abstractSyntaxTree/Expression/LocalVarIdentifier.java
index 9276930..7c1888a 100644
--- a/src/main/java/abstractSyntaxTree/Expression/VarRefExpression.java
+++ b/src/main/java/abstractSyntaxTree/Expression/LocalVarIdentifier.java
@@ -1,15 +1,19 @@
 package abstractSyntaxTree.Expression;
 
+import TypeCheck.TypeCheckHelper;
 import TypeCheck.TypeCheckResult;
 import org.objectweb.asm.MethodVisitor;
 
-import java.util.Map;
+public class LocalVarIdentifier implements IExpression{
 
-public class VarRefExpression implements IExpression{
+    String identifier;
+    public LocalVarIdentifier(String identifier){
+        this.identifier = identifier;
+    }
 
-    //Parameters that are needed here
-    private String varName;
-    private Map<String, Integer> localVars;
+    public String getIdentifier() {
+        return identifier;
+    }
 
     @Override
     public TypeCheckResult typeCheck() throws Exception {
@@ -18,6 +22,6 @@ public class VarRefExpression implements IExpression{
 
     @Override
     public void codeGen(MethodVisitor mv) throws Exception {
-        throw new Exception("CodeGen not implemented for VarRefExpression");
+
     }
 }
diff --git a/src/main/java/abstractSyntaxTree/Expression/UnaryExpression.java b/src/main/java/abstractSyntaxTree/Expression/UnaryExpression.java
index 4acdc53..6fb57f9 100644
--- a/src/main/java/abstractSyntaxTree/Expression/UnaryExpression.java
+++ b/src/main/java/abstractSyntaxTree/Expression/UnaryExpression.java
@@ -12,6 +12,10 @@ import java.util.Objects;
 public class UnaryExpression extends AbstractType implements IExpression{
     public String operator;
     public IDatatype operand;
+    public UnaryExpression(String operator, IDatatype operand){
+        this.operator = operator;
+        this.operand = operand;
+    }
     @Override
     public TypeCheckResult typeCheck() throws Exception {
         TypeCheckResult result = new TypeCheckResult();
@@ -29,12 +33,13 @@ public class UnaryExpression extends AbstractType implements IExpression{
             }
 
             case "-":
-            case "+":
+            case "":
+            case "+":{
                 if (Objects.equals(operandType, "int")){
                     result.type = "int";
                 }
                 break;
-
+            }
         }
 
         setTypeCheckResult(result);
diff --git a/src/main/java/abstractSyntaxTree/Program.java b/src/main/java/abstractSyntaxTree/Program.java
index ed2750e..95ba437 100644
--- a/src/main/java/abstractSyntaxTree/Program.java
+++ b/src/main/java/abstractSyntaxTree/Program.java
@@ -4,6 +4,8 @@ import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Class.FieldDecl;
 import abstractSyntaxTree.Class.MethodDecl;
 import abstractSyntaxTree.Class.RefType;
+import abstractSyntaxTree.Parameter.Parameter;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Opcodes;
 
@@ -18,7 +20,7 @@ import java.util.jar.JarOutputStream;
 public class Program implements Node {
     public List<RefType> classes;
     public HashMap<String, HashMap<String, String>> typeContext; // (class, (type, identifier))
-    public HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext; // (class, (returntype, (identifier, parameter)))
+    public HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext; // (class, (returntype, (identifier, parameter)))
 
     public Program(List<RefType> classes){
         this.classes = classes;
@@ -39,11 +41,11 @@ public class Program implements Node {
             typeContext.put(oneClass.name, classVars);
 
             // build method context
-            HashMap<String, List<String>> methodIdentifierAndParameter = new HashMap<>();
-            HashMap<String, HashMap<String, List<String >>> returnTypeAndMethod = new HashMap<>();
+            HashMap<String, ParameterList> methodIdentifierAndParameter = new HashMap<>();
+            HashMap<String, HashMap<String, ParameterList>> returnTypeAndMethod = new HashMap<>();
             for (MethodDecl methodDecl : oneClass.methodDecls){
 
-                methodIdentifierAndParameter.put(methodDecl.name, (List<String>) methodDecl.parameters);
+                methodIdentifierAndParameter.put(methodDecl.name,  methodDecl.parameters);
                 returnTypeAndMethod.put(methodDecl.returnType, methodIdentifierAndParameter);
             }
             methodContext.put(oneClass.name, returnTypeAndMethod);
diff --git a/src/main/java/abstractSyntaxTree/Statement/BlockStatement.java b/src/main/java/abstractSyntaxTree/Statement/BlockStatement.java
index 039abbb..f0e3645 100644
--- a/src/main/java/abstractSyntaxTree/Statement/BlockStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/BlockStatement.java
@@ -2,6 +2,8 @@ package abstractSyntaxTree.Statement;
 
 import TypeCheck.TypeCheckResult;
 import TypeCheck.AbstractType;
+import abstractSyntaxTree.Class.FieldDecl;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.*;
 
 import java.util.HashMap;
@@ -11,8 +13,8 @@ public class BlockStatement extends AbstractType implements IStatement{
 
     //We will need a parameter which holds the symbol table
     HashMap<String, String > localVars;
-    String returnType;
-    List<IStatement> statements;
+    public String returnType;
+    public List<IStatement> statements;
     // do we need expression, statementexpression
 
     public BlockStatement(List<IStatement> statements, String returnType){
@@ -21,31 +23,24 @@ public class BlockStatement extends AbstractType implements IStatement{
     }
 
     @Override
-    public TypeCheckResult typeCheck() throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext,
+                                     HashMap<String, HashMap<String, String>> typeContext,
+                                     HashMap<String, String> localVars) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
 
         if(statements.size() == 0){
             result.type = "void";
         }
 
-        TypeCheckResult blockType = new TypeCheckResult();
         for (IStatement statement : statements) {
             TypeCheckResult typeOfCurrentStatement = statement.typeCheck(methodContext, typeContext, localVars);
 
-            if (!typeOfCurrentStatement.equals(this.returnType) && !blockType.equals("void")) {
-                throw new IllegalArgumentException("Block returns type that it should not return");
+            if (!typeOfCurrentStatement.type.equals(this.returnType)) {
+                if(!typeOfCurrentStatement.type.equals("void"))
+                    throw new Exception("TypeCheck Exception: Block returns the wrong type.");
             }
         }
+        result.type = this.returnType;
         // todo check if the block returns the needed return type in every case
         // todo ignore unreadchable statements?
         return result;
diff --git a/src/main/java/abstractSyntaxTree/Statement/EmptyStatement.java b/src/main/java/abstractSyntaxTree/Statement/EmptyStatement.java
index 774e0b7..a7ad544 100644
--- a/src/main/java/abstractSyntaxTree/Statement/EmptyStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/EmptyStatement.java
@@ -2,26 +2,16 @@ package abstractSyntaxTree.Statement;
 
 import TypeCheck.TypeCheckResult;
 import TypeCheck.AbstractType;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.MethodVisitor;
 
 import java.util.HashMap;
 import java.util.List;
 
 public class EmptyStatement  extends AbstractType implements IStatement{
-    @Override
-    public TypeCheckResult typeCheck() throws Exception {
-        TypeCheckResult result = new TypeCheckResult();
-        result.type = "void";
-        return result;
-    }
 
     @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return typeCheck(methodContext, typeContext);
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
         result.type = "void";
         return result;
diff --git a/src/main/java/abstractSyntaxTree/Statement/IStatement.java b/src/main/java/abstractSyntaxTree/Statement/IStatement.java
index 85918b5..2225532 100644
--- a/src/main/java/abstractSyntaxTree/Statement/IStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/IStatement.java
@@ -2,6 +2,7 @@ package abstractSyntaxTree.Statement;
 
 import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Node;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.MethodVisitor;
 
 import java.util.HashMap;
@@ -9,15 +10,7 @@ import java.util.List;
 
 public interface IStatement extends Node {
 
-
-
-    TypeCheckResult typeCheck() throws Exception;
-
-    TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception;
-
-
-    TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception;
-
+    TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception;
 
     void codeGen(MethodVisitor mv, HashMap<String, String> localVars) throws Exception;
 }
diff --git a/src/main/java/abstractSyntaxTree/Statement/IfElseStatement.java b/src/main/java/abstractSyntaxTree/Statement/IfElseStatement.java
index b28086b..0a07c93 100644
--- a/src/main/java/abstractSyntaxTree/Statement/IfElseStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/IfElseStatement.java
@@ -3,6 +3,7 @@ package abstractSyntaxTree.Statement;
 import TypeCheck.TypeCheckResult;
 import TypeCheck.AbstractType;
 import abstractSyntaxTree.Expression.IExpression;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.*;
 
 import java.util.HashMap;
@@ -19,8 +20,9 @@ public class IfElseStatement extends AbstractType implements IStatement{
         this.elseStatement = elseStatement;
     }
 
+
     @Override
-    public TypeCheckResult typeCheck() throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
 
         TypeCheckResult conditionType = condition.typeCheck();
@@ -29,8 +31,8 @@ public class IfElseStatement extends AbstractType implements IStatement{
             throw new IllegalArgumentException("should be boolean");
         }
 
-        TypeCheckResult ifStatementType = ifStatement.typeCheck();
-        TypeCheckResult elseStatementType = elseStatement.typeCheck();
+        TypeCheckResult ifStatementType = ifStatement.typeCheck(methodContext, typeContext, localVars);
+        TypeCheckResult elseStatementType = elseStatement.typeCheck(methodContext, typeContext, localVars);
 
         if (!ifStatementType.equals(elseStatementType)) {
             throw new IllegalArgumentException("if and else have different types");
@@ -40,16 +42,6 @@ public class IfElseStatement extends AbstractType implements IStatement{
         return result;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
-        return null;
-    }
-
     @Override
     public void codeGen(MethodVisitor mv, HashMap<String, String> localVars) throws Exception {
 
diff --git a/src/main/java/abstractSyntaxTree/Statement/IfStatement.java b/src/main/java/abstractSyntaxTree/Statement/IfStatement.java
index b51fe74..fc8c22d 100644
--- a/src/main/java/abstractSyntaxTree/Statement/IfStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/IfStatement.java
@@ -3,6 +3,7 @@ package abstractSyntaxTree.Statement;
 import TypeCheck.TypeCheckResult;
 import TypeCheck.AbstractType;
 import abstractSyntaxTree.Expression.IExpression;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.*;
 
 import java.util.HashMap;
@@ -18,8 +19,9 @@ public class IfStatement extends AbstractType implements IStatement{
         this.condition = condition;
         this.ifStatement = ifStatement;
     }
+
     @Override
-    public TypeCheckResult typeCheck() throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
 
         TypeCheckResult conditionType = condition.typeCheck();
@@ -28,21 +30,11 @@ public class IfStatement extends AbstractType implements IStatement{
             throw new Exception("TypeCheck Exception: Condition of If-Statement should be bool.");
         }
 
-        TypeCheckResult ifStatementType = ifStatement.typeCheck();
+        TypeCheckResult ifStatementType = ifStatement.typeCheck(methodContext, typeContext, localVars);
         result.type = ifStatementType.type;
         return result;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
-        return null;
-    }
-
     @Override
     public void codeGen(MethodVisitor mv, HashMap<String, String> localVars) throws Exception {
 
diff --git a/src/main/java/abstractSyntaxTree/Statement/LocalVarDecl.java b/src/main/java/abstractSyntaxTree/Statement/LocalVarDecl.java
new file mode 100644
index 0000000..4fd73a4
--- /dev/null
+++ b/src/main/java/abstractSyntaxTree/Statement/LocalVarDecl.java
@@ -0,0 +1,35 @@
+package abstractSyntaxTree.Statement;
+
+import TypeCheck.TypeCheckHelper;
+import TypeCheck.TypeCheckResult;
+import abstractSyntaxTree.Parameter.ParameterList;
+import org.objectweb.asm.MethodVisitor;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+
+public class LocalVarDecl implements IStatement{
+    String type;
+    String identifier;
+    public LocalVarDecl(String type, String identifier) {
+        this.type = type;
+        this.identifier = identifier;
+    }
+    @Override
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
+        TypeCheckHelper.typeExists(this.type, new ArrayList<>(methodContext.keySet()));
+
+        localVars.put(this.identifier, this.type);
+
+        TypeCheckResult result = new TypeCheckResult();
+        result.type = "void";
+        return result;
+    }
+
+    @Override
+    public void codeGen(MethodVisitor mv, HashMap<String, String> localVars) throws Exception {
+
+    }
+}
diff --git a/src/main/java/abstractSyntaxTree/Statement/ReturnStatement.java b/src/main/java/abstractSyntaxTree/Statement/ReturnStatement.java
index 8e324d7..358ee25 100644
--- a/src/main/java/abstractSyntaxTree/Statement/ReturnStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/ReturnStatement.java
@@ -3,6 +3,7 @@ package abstractSyntaxTree.Statement;
 import TypeCheck.TypeCheckResult;
 import TypeCheck.AbstractType;
 import abstractSyntaxTree.Expression.IExpression;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.*;
 
 import java.util.HashMap;
@@ -16,7 +17,7 @@ public class ReturnStatement extends AbstractType implements IStatement{
     }
 
     @Override
-    public TypeCheckResult typeCheck() throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
 
         if (expression == null) {
@@ -29,17 +30,6 @@ public class ReturnStatement extends AbstractType implements IStatement{
         return result;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
-        return null;
-    }
-
-
     //TODO: We do not differentiate between primitive types and reference types
     //      This is a problem at "BinaryExpression" and here because we need to know the type to return
     //      At this point in time we can either return reference types or have an error message
diff --git a/src/main/java/abstractSyntaxTree/Statement/WhileStatement.java b/src/main/java/abstractSyntaxTree/Statement/WhileStatement.java
index b312be3..02d19e3 100644
--- a/src/main/java/abstractSyntaxTree/Statement/WhileStatement.java
+++ b/src/main/java/abstractSyntaxTree/Statement/WhileStatement.java
@@ -3,6 +3,7 @@ package abstractSyntaxTree.Statement;
 import TypeCheck.TypeCheckResult;
 import TypeCheck.AbstractType;
 import abstractSyntaxTree.Expression.IExpression;
+import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.*;
 
 import java.util.HashMap;
@@ -18,7 +19,7 @@ public class WhileStatement extends AbstractType implements IStatement {
     }
 
     @Override
-    public TypeCheckResult typeCheck() throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         TypeCheckResult result = new TypeCheckResult();
 
         TypeCheckResult conditionType = condition.typeCheck();
@@ -27,22 +28,12 @@ public class WhileStatement extends AbstractType implements IStatement {
             throw new IllegalArgumentException("Expected boolean");
         }
 
-        TypeCheckResult statementType = statement.typeCheck();
+        TypeCheckResult statementType = statement.typeCheck(methodContext, typeContext, localVars);
 
         result.type = statementType.type;
         return result;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
-        return null;
-    }
-
     @Override
     public void codeGen(MethodVisitor mv, HashMap<String, String> localVars) throws Exception {
         Label conditionFalse = new Label();
diff --git a/src/main/java/abstractSyntaxTree/StatementExpression/AssignStatementExpression.java b/src/main/java/abstractSyntaxTree/StatementExpression/AssignStatementExpression.java
index 8d96ae6..369557f 100644
--- a/src/main/java/abstractSyntaxTree/StatementExpression/AssignStatementExpression.java
+++ b/src/main/java/abstractSyntaxTree/StatementExpression/AssignStatementExpression.java
@@ -5,12 +5,12 @@ import TypeCheck.TypeCheckHelper;
 import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Expression.IExpression;
 import abstractSyntaxTree.Expression.InstVarExpression;
-import abstractSyntaxTree.Expression.VarRefExpression;
+import abstractSyntaxTree.Expression.LocalVarIdentifier;
+import abstractSyntaxTree.Parameter.ParameterList;
 import abstractSyntaxTree.Statement.IStatement;
 import org.objectweb.asm.*;
 
 import java.util.HashMap;
-import java.util.List;
 import java.util.Objects;
 
 public class AssignStatementExpression extends AbstractType implements IExpression, IStatement {
@@ -18,12 +18,27 @@ public class AssignStatementExpression extends AbstractType implements IExpressi
     public IExpression left;
     public IExpression right;
 
+    public AssignStatementExpression(String operator, IExpression leftExpression, IExpression rightExpression){
+        this.operator = operator;
+        this.left = leftExpression;
+        this.right = rightExpression;
+    }
+
     @Override
-    public TypeCheckResult typeCheck() throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         TypeCheckHelper helper = new TypeCheckHelper();
         TypeCheckResult result = new TypeCheckResult();
 
         TypeCheckResult leftType = left.typeCheck();
+        if(leftType == null){ //left expression is the identifier of a var
+            leftType = new TypeCheckResult();
+            if (left instanceof LocalVarIdentifier) {
+                LocalVarIdentifier localVarIdentifier = (LocalVarIdentifier) left;
+                String identifier = localVarIdentifier.getIdentifier();
+                leftType.type = localVars.get(identifier);
+            }
+            // not local var
+        }
         TypeCheckResult rightType = right.typeCheck();
 
         String upperbound = helper.upperBound(leftType.type, rightType.type);
@@ -34,21 +49,16 @@ public class AssignStatementExpression extends AbstractType implements IExpressi
         return result;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
-
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
-        return null;
-    }
-
     @Override
     public void codeGen(MethodVisitor mv, HashMap<String, String> localVars) throws Exception {
 
     }
 
+    @Override
+    public TypeCheckResult typeCheck() throws Exception {
+        return null;
+    }
+
     @Override
     public void codeGen(MethodVisitor mv) throws Exception {
         left.codeGen(mv);
diff --git a/src/main/java/abstractSyntaxTree/StatementExpression/MethodCallStatementExpression.java b/src/main/java/abstractSyntaxTree/StatementExpression/MethodCallStatementExpression.java
index 1e6598a..0540422 100644
--- a/src/main/java/abstractSyntaxTree/StatementExpression/MethodCallStatementExpression.java
+++ b/src/main/java/abstractSyntaxTree/StatementExpression/MethodCallStatementExpression.java
@@ -5,6 +5,7 @@ import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Class.MethodDecl;
 import abstractSyntaxTree.Class.RefType;
 import abstractSyntaxTree.Expression.IExpression;
+import abstractSyntaxTree.Parameter.ParameterList;
 import abstractSyntaxTree.Statement.IStatement;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.MethodVisitor;
@@ -44,13 +45,9 @@ public class MethodCallStatementExpression extends AbstractType implements IExpr
         return result;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
 
     @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         return null;
     }
 
diff --git a/src/main/java/abstractSyntaxTree/StatementExpression/NewStatementExpression.java b/src/main/java/abstractSyntaxTree/StatementExpression/NewStatementExpression.java
index 63b7743..da19394 100644
--- a/src/main/java/abstractSyntaxTree/StatementExpression/NewStatementExpression.java
+++ b/src/main/java/abstractSyntaxTree/StatementExpression/NewStatementExpression.java
@@ -3,6 +3,7 @@ package abstractSyntaxTree.StatementExpression;
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Expression.IExpression;
+import abstractSyntaxTree.Parameter.ParameterList;
 import abstractSyntaxTree.Statement.IStatement;
 import org.objectweb.asm.MethodVisitor;
 
@@ -15,13 +16,10 @@ public class NewStatementExpression extends AbstractType implements IExpression,
         return null;
     }
 
-    @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
-        return null;
-    }
+
 
     @Override
-    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, List<String>>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    public TypeCheckResult typeCheck(HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, String> localVars) throws Exception {
         return null;
     }