diff --git a/Test/Aufgabe2_KellerautomatTest.java b/Test/Aufgabe2_KellerautomatTest.java
new file mode 100644
index 0000000..961bdff
--- /dev/null
+++ b/Test/Aufgabe2_KellerautomatTest.java
@@ -0,0 +1,14 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class Aufgabe2_KellerautomatTest {
+
+    @Test
+    void calculate() {
+        assertEquals('Z', Aufgabe2_Kellerautomat.calculate("ZZ+ZZ+ZZ+ZZ+***"));
+        assertEquals('Z', Aufgabe2_Kellerautomat.calculate("ZZ+ZZ+ZZZ+ZZZZ++Z++++++"));
+        assertEquals('$', Aufgabe2_Kellerautomat.calculate("ZZ+*"));
+        assertEquals('$', Aufgabe2_Kellerautomat.calculate("Z+Z+Z*Z*"));
+    }
+}
\ No newline at end of file
diff --git a/src/Kellerautomat.java b/src/Aufgabe2_Kellerautomat.java
similarity index 76%
rename from src/Kellerautomat.java
rename to src/Aufgabe2_Kellerautomat.java
index 913c25f..f0a015f 100644
--- a/src/Kellerautomat.java
+++ b/src/Aufgabe2_Kellerautomat.java
@@ -3,7 +3,7 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
-public class Kellerautomat {
+public class Aufgabe2_Kellerautomat {
     private static String[] words = {"ZZO", "ZZOZZOO", "ZZZOO", "ZZOO", "ZZOZZO", "ZOZ"};
 
     public static void main(String[] args) {
@@ -12,7 +12,7 @@ public class Kellerautomat {
         }
     }
 
-    public static boolean calculate(String word) {
+    public static char calculate(String word) {
         List<Character> wordChars = new ArrayList<>();
         for (char symbol : word.toCharArray()) {
             wordChars.add(symbol);
@@ -21,6 +21,10 @@ public class Kellerautomat {
         stack.add('$');
 
         int state = 0; //case 0 - 5 = q0 - q5, case -1 = Abfallzustand
+        char operator = '$';
+        char firstNumber = '$';
+        char secondNumber = '$';
+        char result = '$';
 
         while (wordChars.size() > 0 || state >= 3) {
             char symbol;
@@ -33,7 +37,7 @@ public class Kellerautomat {
                         state = 1;
                     } else {
                         dontAccept(word);
-                        return false;
+                        return '$';
                     }
                     break;
                 case 1:
@@ -43,12 +47,14 @@ public class Kellerautomat {
                         state = 2;
                     } else {
                         dontAccept(word);
-                        return false;
+                        return '$';
                     }
                     break;
                 case 2:
                     symbol = wordChars.remove(0);
-                    if (symbol == 'O' && stackSymbol == 'Z') {
+                    if (isOperator(symbol) && stackSymbol == 'Z') {
+                        operator = symbol;
+                        firstNumber = stackSymbol;
                         state = 3;
                     } else if (symbol == 'Z' && stackSymbol == 'Z') {
                         stack.add('Z');
@@ -60,16 +66,17 @@ public class Kellerautomat {
                         state = 2;
                     } else {
                         dontAccept(word);
-                        return false;
+                        return '$';
                     }
                     break;
                 case 3:
                     if (stackSymbol == 'Z') {
-                        stack.add('Z');
+                        secondNumber = stackSymbol;
+                        stack.add(doOperation(operator, firstNumber, secondNumber));
                         state = 4;
                     } else {
                         dontAccept(word);
-                        return false;
+                        return '$';
                     }
                     break;
                 case 4:
@@ -79,18 +86,21 @@ public class Kellerautomat {
                             stack.add('Z');
                             stack.add('Z');
                             state = 2;
-                        } else if (symbol == 'O' && stackSymbol == 'Z') {
+                        } else if (isOperator(symbol) && stackSymbol == 'Z') {
+                            operator = symbol;
+                            firstNumber = stackSymbol;
                             state = 3;
                         } else {
                             dontAccept(word);
-                            return false;
+                            return '$';
                         }
                     } else {
                         if (stackSymbol == 'Z') {
+                            result = stackSymbol;
                             state = 5;
                         } else {
                             dontAccept(word);
-                            return false;
+                            return '$';
                         }
                     }
                     break;
@@ -100,17 +110,17 @@ public class Kellerautomat {
                         state = 6;
                     } else {
                         dontAccept(word);
-                        return false;
+                        return '$';
                     }
                     break;
                 case 6:
                     accept(word);
-                    return true;
+                    return result;
 
             }
         }
         dontAccept(word);
-        return false;
+        return '$';
     }
 
     private static void dontAccept(String word) {
@@ -125,4 +135,8 @@ public class Kellerautomat {
         return symbol == '+' || symbol == '*';
     }
 
+    private static char doOperation(char doOperation, char firstNumber, char secondNumber){
+        return 'Z';
+    }
+
 }