diff --git a/src/main/java/ast/block/BlockNode.java b/src/main/java/ast/block/BlockNode.java
index 9987cf9..ab2d70b 100644
--- a/src/main/java/ast/block/BlockNode.java
+++ b/src/main/java/ast/block/BlockNode.java
@@ -2,6 +2,7 @@ package ast.block;
 
 import ast.ASTNode;
 import ast.statement.IStatementNode;
+import ast.statement.ReturnStatementNode;
 import semantic.SemanticVisitor;
 import typechecker.TypeCheckResult;
 import visitor.Visitable;
@@ -12,6 +13,7 @@ import java.util.List;
 
 public class BlockNode implements ASTNode, Visitable {
     public List<IStatementNode> statements = new ArrayList<>();
+    public Boolean hasReturnStatement = false;
 
     public BlockNode() {}
 
diff --git a/src/main/java/ast/expression/binaryexpression/CalculationExpressionNode.java b/src/main/java/ast/expression/binaryexpression/CalculationExpressionNode.java
index 70451d8..b594502 100644
--- a/src/main/java/ast/expression/binaryexpression/CalculationExpressionNode.java
+++ b/src/main/java/ast/expression/binaryexpression/CalculationExpressionNode.java
@@ -6,12 +6,12 @@ import typechecker.TypeCheckResult;
 
 public class CalculationExpressionNode extends BinaryExpressionNode {
     public CalculationExpressionNode calculationExpression;
-    public String operator;
+    public EnumLineOperator operator;
     public DotExpressionNode dotExpression;
 
     public CalculationExpressionNode(CalculationExpressionNode calculationExpression, String operator, DotExpressionNode dotExpression) {
         this.calculationExpression = calculationExpression;
-        this.operator = operator;
+        setOperator(operator);
         this.dotExpression = dotExpression;
     }
 
@@ -19,6 +19,14 @@ public class CalculationExpressionNode extends BinaryExpressionNode {
         this.dotExpression = dotExpression;
     }
 
+    private void setOperator(String operator) {
+        if(operator.equals("+")) {
+            this.operator = EnumLineOperator.PLUS;
+        } else if(operator.equals("-")) {
+            this.operator = EnumLineOperator.MINUS;
+        }
+    }
+
     @Override
     public TypeCheckResult accept(SemanticVisitor visitor) {
         return visitor.analyze(this);
diff --git a/src/main/java/ast/expression/binaryexpression/DotExpressionNode.java b/src/main/java/ast/expression/binaryexpression/DotExpressionNode.java
index cc5f2c6..2d56221 100644
--- a/src/main/java/ast/expression/binaryexpression/DotExpressionNode.java
+++ b/src/main/java/ast/expression/binaryexpression/DotExpressionNode.java
@@ -6,12 +6,12 @@ import typechecker.TypeCheckResult;
 
 public class DotExpressionNode extends BinaryExpressionNode {
     public DotExpressionNode dotExpression;
-    public String operator;
+    public EnumDotOperator operator;
     public DotSubstractionExpressionNode dotSubstractionExpression;
 
     public DotExpressionNode(DotExpressionNode dotExpression, String operator, DotSubstractionExpressionNode dotSubstractionExpression) {
         this.dotExpression = dotExpression;
-        this.operator = operator;
+        setOperator(operator);
         this.dotSubstractionExpression = dotSubstractionExpression;
     }
 
@@ -19,6 +19,16 @@ public class DotExpressionNode extends BinaryExpressionNode {
         this.dotSubstractionExpression = dotSubstractionExpression;
     }
 
+    private void setOperator(String operator) {
+        if(operator.equals("*")) {
+            this.operator = EnumDotOperator.MULT;
+        } else if(operator.equals("/")) {
+            this.operator = EnumDotOperator.DIV;
+        } else if(operator.equals("%")) {
+            this.operator = EnumDotOperator.MOD;
+        }
+    }
+
     @Override
     public TypeCheckResult accept(SemanticVisitor visitor) {
         return visitor.analyze(this);
diff --git a/src/main/java/ast/expression/binaryexpression/EnumDotOperator.java b/src/main/java/ast/expression/binaryexpression/EnumDotOperator.java
new file mode 100644
index 0000000..3525266
--- /dev/null
+++ b/src/main/java/ast/expression/binaryexpression/EnumDotOperator.java
@@ -0,0 +1,5 @@
+package ast.expression.binaryexpression;
+
+public enum EnumDotOperator {
+    MULT, DIV, MOD
+}
diff --git a/src/main/java/ast/expression/binaryexpression/EnumLineOperator.java b/src/main/java/ast/expression/binaryexpression/EnumLineOperator.java
new file mode 100644
index 0000000..27389ec
--- /dev/null
+++ b/src/main/java/ast/expression/binaryexpression/EnumLineOperator.java
@@ -0,0 +1,5 @@
+package ast.expression.binaryexpression;
+
+public enum EnumLineOperator {
+    PLUS, MINUS
+}
diff --git a/src/main/java/ast/expression/binaryexpression/EnumNonCalculationOperator.java b/src/main/java/ast/expression/binaryexpression/EnumNonCalculationOperator.java
new file mode 100644
index 0000000..40c3dfd
--- /dev/null
+++ b/src/main/java/ast/expression/binaryexpression/EnumNonCalculationOperator.java
@@ -0,0 +1,5 @@
+package ast.expression.binaryexpression;
+
+public enum EnumNonCalculationOperator {
+    AND, OR, GREATER, LESS, GREATER_EQUAL, LESS_EQUAL, EQUAL, NOT_EQUAL
+}
diff --git a/src/main/java/ast/expression/binaryexpression/NonCalculationExpressionNode.java b/src/main/java/ast/expression/binaryexpression/NonCalculationExpressionNode.java
index 5cdebc2..f89fdf8 100644
--- a/src/main/java/ast/expression/binaryexpression/NonCalculationExpressionNode.java
+++ b/src/main/java/ast/expression/binaryexpression/NonCalculationExpressionNode.java
@@ -8,15 +8,35 @@ import typechecker.TypeCheckResult;
 
 public class NonCalculationExpressionNode extends BinaryExpressionNode {
     public UnaryExpressionNode unaryExpression;
-    public String operator;
+    public EnumNonCalculationOperator operator;
     public IExpressionNode expression;
 
     public NonCalculationExpressionNode(UnaryExpressionNode unaryExpression, String operator, IExpressionNode expression) {
         this.unaryExpression = unaryExpression;
-        this.operator = operator;
+        setOperator(operator);
         this.expression = expression;
     }
 
+    private void setOperator(String operator) {
+        if(operator.equals("&&")) {
+            this.operator = EnumNonCalculationOperator.AND;
+        } else if(operator.equals("||")) {
+            this.operator = EnumNonCalculationOperator.OR;
+        } else if(operator.equals(">")) {
+            this.operator = EnumNonCalculationOperator.GREATER;
+        } else if(operator.equals("<")) {
+            this.operator = EnumNonCalculationOperator.LESS;
+        } else if(operator.equals(">=")) {
+            this.operator = EnumNonCalculationOperator.GREATER_EQUAL;
+        } else if(operator.equals("<=")) {
+            this.operator = EnumNonCalculationOperator.LESS_EQUAL;
+        } else if(operator.equals("==")) {
+            this.operator = EnumNonCalculationOperator.EQUAL;
+        } else if(operator.equals("!=")) {
+            this.operator = EnumNonCalculationOperator.NOT_EQUAL;
+        }
+    }
+
     @Override
     public TypeCheckResult accept(SemanticVisitor visitor) {
         return visitor.analyze(this);
diff --git a/src/main/java/ast/member/MainMethodNode.java b/src/main/java/ast/member/MainMethodNode.java
new file mode 100644
index 0000000..e50cc4f
--- /dev/null
+++ b/src/main/java/ast/member/MainMethodNode.java
@@ -0,0 +1,11 @@
+package ast.member;
+
+import ast.block.BlockNode;
+
+public class MainMethodNode extends MethodNode {
+    public BlockNode block;
+
+    public MainMethodNode(BlockNode block) {
+        this.block = block;
+    }
+}
diff --git a/src/main/java/ast/member/MethodNode.java b/src/main/java/ast/member/MethodNode.java
index ecfd598..2aecf57 100644
--- a/src/main/java/ast/member/MethodNode.java
+++ b/src/main/java/ast/member/MethodNode.java
@@ -23,10 +23,6 @@ public class MethodNode implements MemberNode, Visitable {
 
     public MethodNode() {}
 
-    public MethodNode(BlockNode block){
-        this.block = block;
-    }
-
     public MethodNode(String accessModifier, ITypeNode type, Boolean voidType, String identifier, BlockNode block){
         this.accesModifier = new AccessModifierNode(accessModifier);
         this.type = type;
diff --git a/src/main/java/ast/statement/ReturnStatementNode.java b/src/main/java/ast/statement/ReturnStatementNode.java
index 66d3846..e525c3f 100644
--- a/src/main/java/ast/statement/ReturnStatementNode.java
+++ b/src/main/java/ast/statement/ReturnStatementNode.java
@@ -1,15 +1,19 @@
 package ast.statement;
 
-import ast.ASTNode;
 import ast.expression.IExpressionNode;
 import semantic.SemanticVisitor;
 import typechecker.TypeCheckResult;
 
 public class ReturnStatementNode implements IStatementNode {
     public IExpressionNode expression;
+    public Boolean voidReturn = false;
 
     public ReturnStatementNode(IExpressionNode expression) {
-        this.expression = expression;
+        if(expression != null) {
+            this.expression = expression;
+        } else {
+            voidReturn = true;
+        }
     }
 
     @Override
diff --git a/src/main/java/ast/type/EnumTypeNode.java b/src/main/java/ast/type/EnumTypeNode.java
deleted file mode 100644
index 98c38ea..0000000
--- a/src/main/java/ast/type/EnumTypeNode.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package ast.type;
-
-public enum EnumTypeNode {
-    INT, BOOLEAN, CHAR, IDENTIFIER
-}
diff --git a/src/main/java/parser/astBuilder/ASTBuilder.java b/src/main/java/parser/astBuilder/ASTBuilder.java
index 31a8b82..95ac93c 100644
--- a/src/main/java/parser/astBuilder/ASTBuilder.java
+++ b/src/main/java/parser/astBuilder/ASTBuilder.java
@@ -10,12 +10,9 @@ import ast.expression.binaryexpression.NonCalculationExpressionNode;
 import ast.expression.unaryexpression.MemberAccessNode;
 import ast.expression.unaryexpression.NotExpressionNode;
 import ast.expression.unaryexpression.UnaryExpressionNode;
-import ast.member.FieldNode;
-import ast.member.MethodNode;
+import ast.member.*;
 import ast.statement.ifstatement.ElseStatementNode;
 import ast.statement.ifstatement.IfElseStatementNode;
-import ast.member.ConstructorNode;
-import ast.member.MemberNode;
 import ast.parameter.ParameterNode;
 import ast.statement.*;
 import ast.statement.ifstatement.IfStatementNode;
@@ -65,7 +62,7 @@ public class ASTBuilder extends SimpleJavaBaseVisitor<ASTNode> {
     @Override
     public ASTNode visitMethodDeclaration(SimpleJavaParser.MethodDeclarationContext ctx) {
         if(ctx.MainMethodDeclaration() != null) {
-            return new MethodNode((BlockNode) visit(ctx.block()));
+            return new MainMethodNode((BlockNode) visit(ctx.block()));
         } else {
             if(ctx.type() != null) {
                 MethodNode methodNode = new MethodNode(ctx.AccessModifier().getText(), createTypeNode(ctx.type().getText()), false, ctx.Identifier().getText(), (BlockNode) visit(ctx.block()));
@@ -129,6 +126,9 @@ public class ASTBuilder extends SimpleJavaBaseVisitor<ASTNode> {
         for(SimpleJavaParser.StatementContext statement : ctx.statement()) {
             blockNode.addStatement((IStatementNode) visit(statement));
         }
+        if(!blockNode.hasReturnStatement) {
+            blockNode.addStatement(new ReturnStatementNode(null));
+        }
         return blockNode;
     }