diff --git a/src/main/java/de/dhbwstuttgart/parser/scope/GatherNames.java b/src/main/java/de/dhbwstuttgart/parser/scope/GatherNames.java
index 8e93355b..aec9f8b4 100644
--- a/src/main/java/de/dhbwstuttgart/parser/scope/GatherNames.java
+++ b/src/main/java/de/dhbwstuttgart/parser/scope/GatherNames.java
@@ -43,7 +43,7 @@ public class GatherNames {
 	      }
 	      else{
 	        if(typeDecl.classDeclaration().normalClassDeclaration() != null){
-	          if(pkgName != ""){
+	          if(!pkgName.isEmpty()){
 	            nameString = pkgName + "." + typeDecl.classDeclaration().normalClassDeclaration().Identifier().toString();
 	          }
 	          else{
diff --git a/src/main/java/de/dhbwstuttgart/syntaxtree/type/TypePlaceholder.java b/src/main/java/de/dhbwstuttgart/syntaxtree/type/TypePlaceholder.java
index cdc204b0..66435b68 100644
--- a/src/main/java/de/dhbwstuttgart/syntaxtree/type/TypePlaceholder.java
+++ b/src/main/java/de/dhbwstuttgart/syntaxtree/type/TypePlaceholder.java
@@ -64,6 +64,10 @@ public class TypePlaceholder extends RefTypeOrTPHOrWildcardOrGeneric
         }
     }
 
+    @Override
+    public int hashCode() {
+        return this.getName().hashCode();
+    }
 
     public String toString()
     {
diff --git a/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyType.java b/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyType.java
index f7ded0a6..8d253092 100644
--- a/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyType.java
+++ b/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyType.java
@@ -114,6 +114,7 @@ public abstract class UnifyType {
 
 	@Override
 	public boolean equals(Object obj) {
+		if(obj == null)return false;
 		return this.toString().equals(obj.toString());
 	}
 }
\ No newline at end of file