diff --git a/src/main/scala/hb/dhbw/FJTypeinference.scala b/src/main/scala/hb/dhbw/FJTypeinference.scala
index 752a603..e7ffc4f 100644
--- a/src/main/scala/hb/dhbw/FJTypeinference.scala
+++ b/src/main/scala/hb/dhbw/FJTypeinference.scala
@@ -56,9 +56,11 @@ object FJTypeinference {
       if(m.params.size != superMethod.params.size){
         false
       }else{
-        var returnIsSub = finiteClosure.aIsSubtypeOfb(convertToFJType(getBound(m.retType)), convertToFJType(getBound(superMethod.retType)))
-        returnIsSub && m.params.zip(superMethod.params).foldLeft(true)((isSub, m2) =>
-          isSub && finiteClosure.aIsSubtypeOfb(convertToFJType(getBound(m2._1._1)), convertToFJType(getBound(m2._2._1))))
+        val returnIsSub = finiteClosure.aIsSubtypeOfb(convertToFJType(getBound(m.retType)), convertToFJType(getBound(superMethod.retType)))
+        val paramsAreSup = m.params.zip(superMethod.params).foldLeft(true)((isSub, m2) => {
+          isSub && finiteClosure.aIsSubtypeOfb(convertToFJType(getBound(m2._2._1)), convertToFJType(getBound(m2._1._1)))
+        })
+        returnIsSub && paramsAreSup
       }
     }
 
@@ -69,7 +71,7 @@ object FJTypeinference {
         if(ms.find(methodIsSupertype(_, m)).isDefined) { //If there is a method which is more general
           ms //do not add this method
         }else { //otherwise check if this method shadows another method
-          ms.filter(methodIsSupertype(m, _)) + m
+          ms.filter(!methodIsSupertype(m, _)) + m
         }
       })
     })
diff --git a/src/test/scala/IntegrationTest.scala b/src/test/scala/IntegrationTest.scala
index 88eab65..99fc8ee 100644
--- a/src/test/scala/IntegrationTest.scala
+++ b/src/test/scala/IntegrationTest.scala
@@ -102,8 +102,32 @@ class IntegrationTest extends FunSuite {
     val result = FJTypeinference.typeinference(input)
     println(result.map(it => Main.prettyPrintAST(it._2)))
   }
+
+  test("PrincipalType") {
+    val input = "\nclass List<A extends Object> extends Object{\n  A head;\n  List<A> tail;\n  add( a){\n    return new List(a, this);\n  }\n  get(){\n    return this.head;\n  }\n}\n\nclass PrincipleType extends Object {\n  function(a){\n    return a.add(this).get();\n  }\n}"
+    val result = FJTypeinference.typeinference(input)
+    println(result.map(it => Main.prettyPrintAST(it._2)))
+  }
   /*
 
+class List<A extends Object> extends Object{
+  A head;
+  List<A> tail;
+  add( a){
+    return new List(a, this);
+  }
+  get(){
+    return this.head;
+  }
+}
+
+class PrincipleType extends Object {
+  function(a){
+    return a.add(this).get();
+  }
+}
+
+
 class Function<A extends Object, B extends Object> extends Object{
 B b;
 B apply(A a){