diff --git a/src/de/dhbwstuttgart/core/JavaTXCompiler.java b/src/de/dhbwstuttgart/core/JavaTXCompiler.java
index 8c43c826..f31255e0 100644
--- a/src/de/dhbwstuttgart/core/JavaTXCompiler.java
+++ b/src/de/dhbwstuttgart/core/JavaTXCompiler.java
@@ -3,16 +3,19 @@ package de.dhbwstuttgart.core;
 
 import de.dhbwstuttgart.environment.CompilationEnvironment;
 import de.dhbwstuttgart.parser.JavaTXParser;
+import de.dhbwstuttgart.parser.NullToken;
 import de.dhbwstuttgart.parser.scope.GenericsRegistry;
 import de.dhbwstuttgart.parser.SyntaxTreeGenerator.SyntaxTreeGenerator;
 import de.dhbwstuttgart.parser.antlr.Java8Parser.CompilationUnitContext;
 import de.dhbwstuttgart.parser.scope.JavaClassName;
 import de.dhbwstuttgart.parser.scope.JavaClassRegistry;
 import de.dhbwstuttgart.syntaxtree.ClassOrInterface;
+import de.dhbwstuttgart.syntaxtree.ParameterList;
 import de.dhbwstuttgart.syntaxtree.SourceFile;
 import de.dhbwstuttgart.syntaxtree.factory.ASTFactory;
 import de.dhbwstuttgart.syntaxtree.factory.UnifyTypeFactory;
 import de.dhbwstuttgart.syntaxtree.type.TypePlaceholder;
+import de.dhbwstuttgart.syntaxtree.visual.ASTTypePrinter;
 import de.dhbwstuttgart.typeinference.constraints.Constraint;
 import de.dhbwstuttgart.typeinference.constraints.ConstraintSet;
 import de.dhbwstuttgart.typeinference.constraints.Pair;
@@ -21,6 +24,7 @@ import de.dhbwstuttgart.typeinference.typeAlgo.TYPE;
 import de.dhbwstuttgart.typeinference.unify.RuleSet;
 import de.dhbwstuttgart.typeinference.unify.TypeUnify;
 import de.dhbwstuttgart.typeinference.unify.model.FiniteClosure;
+import de.dhbwstuttgart.typeinference.unify.model.PlaceholderType;
 import de.dhbwstuttgart.typeinference.unify.model.UnifyPair;
 
 import java.io.File;
@@ -28,6 +32,7 @@ import java.io.FileWriter;
 import java.io.IOException;
 import java.util.*;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 public class JavaTXCompiler {
 
@@ -99,14 +104,53 @@ public class JavaTXCompiler {
         try {
 			FileWriter logFile = new FileWriter(new File(System.getProperty("user.dir")+"/test/logFiles/"+"log"));
 			logFile.write("FC:\\" + finiteClosure.toString()+"\n");
+			for(SourceFile sf : this.sourceFiles.values()) {
+				logFile.write(ASTTypePrinter.print(sf));
+			}
 			logFile.flush();
 			for (List<Constraint<UnifyPair>> xCons : unifyCons.cartesianProduct()) {
 				Set<UnifyPair> xConsSet = new HashSet<>();
 				for (Constraint<UnifyPair> constraint : xCons) {
 					xConsSet.addAll(constraint);
 				}
-
+				//.collect(Collectors.toCollection(ArrayList::new))))
 				System.out.println(xConsSet);
+				Set<String> paraTypeVarNames = allClasses.stream().map(x -> x.getMethods().stream().map(y -> y.getParameterList().getFormalparalist()
+						.stream().filter(z -> z.getType() instanceof TypePlaceholder)
+						.map(z -> ((TypePlaceholder)z.getType()).getName()).collect(Collectors.toCollection(HashSet::new))).reduce((a,b) -> { a.addAll(b); return a;} ).get())
+						.reduce((a,b) -> { a.addAll(b); return a;} ).get();
+				
+				Set<String> returnTypeVarNames = allClasses.stream().map(x -> x.getMethods().stream().filter(y -> y.getReturnType() instanceof TypePlaceholder)
+						.map(z -> ((TypePlaceholder)z.getReturnType()).getName()).collect(Collectors.toCollection(HashSet::new))).reduce((a,b) -> { a.addAll(b); return a;} ).get();
+				
+				
+				xConsSet = xConsSet.stream().map(x -> { 
+					if ((x.getLhsType() instanceof PlaceholderType)) {
+						if (paraTypeVarNames.contains(x.getLhsType().getName()) 
+								&& (!(x.getRhsType() instanceof PlaceholderType) 
+										|| ((x.getRhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getRhsType().getName()) && !returnTypeVarNames.contains(x.getRhsType().getName())))) {
+							x.setVariance((byte)1);
+						}
+						if (returnTypeVarNames.contains(x.getLhsType().getName()) 
+								&& (!(x.getRhsType() instanceof PlaceholderType) 
+										|| ((x.getRhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getRhsType().getName()) && !returnTypeVarNames.contains(x.getRhsType().getName())))) {
+							x.setVariance((byte)-1);
+						}
+					}
+					if ((x.getRhsType() instanceof PlaceholderType)) {
+							if (paraTypeVarNames.contains(x.getRhsType().getName()) 
+									&& (!(x.getLhsType() instanceof PlaceholderType) 
+											|| ((x.getLhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getLhsType().getName()) && !returnTypeVarNames.contains(x.getLhsType().getName())))) {
+								x.setVariance((byte)1);
+							}
+							if (returnTypeVarNames.contains(x.getRhsType().getName()) 
+									&& (!(x.getLhsType() instanceof PlaceholderType) 
+											|| ((x.getLhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getLhsType().getName()) && !returnTypeVarNames.contains(x.getLhsType().getName())))) {
+								x.setVariance((byte)-1);
+							}	
+					}
+					return x;
+				}).collect(Collectors.toCollection(HashSet::new));
     				Set<Set<UnifyPair>> result = unify.unifySequential(xConsSet, finiteClosure, logFile);
     				//Set<Set<UnifyPair>> result = unify.unify(xConsSet, finiteClosure);
     				System.out.println("RESULT: " + result);
diff --git a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
index 73f6eff9..ec383afe 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
@@ -103,7 +103,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		 * Step 1: Repeated application of reduce, adapt, erase, swap 
 		 */
 		writeLog("Unifikation: " + eq.toString());
-		eq = eq.stream().map(x -> {x.setVariance((byte)-1); return x;}).collect(Collectors.toCollection(HashSet::new));
+		//eq = eq.stream().map(x -> {x.setVariance((byte)-1); return x;}).collect(Collectors.toCollection(HashSet::new));
 		Set<UnifyPair> eq0 = applyTypeUnificationRules(eq, fc);
 
 		/*
@@ -311,6 +311,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 	Set<Set<UnifyPair>> computeCartesianRecursive(Set<Set<UnifyPair>> fstElems, ArrayList<Set<Set<UnifyPair>>> topLevelSets, Set<UnifyPair> eq, IFiniteClosure fc, boolean parallel) {
 		ArrayList<Set<Set<UnifyPair>>> remainingSets = new ArrayList<>(topLevelSets);
 		Set<Set<UnifyPair>> nextSet = remainingSets.remove(0);
+		writeLog("nextSet: " + nextSet.toString());
 		List<Set<UnifyPair>> nextSetasList = oup.sortedCopy(nextSet);//new ArrayList<>(nextSet);
 		Set<Set<UnifyPair>> result = new HashSet<>(); 
 		byte variance = 	nextSetasList.iterator().next().iterator().next().getVariance();	
@@ -610,7 +611,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 			if(pairOp == PairOperator.SMALLERDOT && lhsType instanceof PlaceholderType) {
 				//System.out.println(pair);
 				if (first) { //writeLog(pair.toString()+"\n");
-					Set<Set<UnifyPair>> x1 = unifyCase1((PlaceholderType) pair.getLhsType(), pair.getRhsType(), (byte)1, fc);
+					Set<Set<UnifyPair>> x1 = unifyCase1((PlaceholderType) pair.getLhsType(), pair.getRhsType(), pair.getVariance(), fc);
 				//System.out.println(x1);
 					result.get(0).add(x1);
 				}
@@ -626,7 +627,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 			// Case 2: (a <.? ? ext Theta')
 			else if(pairOp == PairOperator.SMALLERDOTWC && lhsType instanceof PlaceholderType && rhsType instanceof ExtendsType)
 				if (first) { //writeLog(pair.toString()+"\n");
-					result.get(1).add(unifyCase2((PlaceholderType) pair.getLhsType(), (ExtendsType) pair.getRhsType(), (byte)0, fc));
+					result.get(1).add(unifyCase2((PlaceholderType) pair.getLhsType(), (ExtendsType) pair.getRhsType(), pair.getVariance(), fc));
 				}	
 				else {
 					Set<UnifyPair> s1 = new HashSet<>();
@@ -639,7 +640,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 			// Case 3: (a <.? ? sup Theta')
 			else if(pairOp == PairOperator.SMALLERDOTWC && lhsType instanceof PlaceholderType && rhsType instanceof SuperType)
 				if (first) { //writeLog(pair.toString()+"\n");
-					result.get(2).add(unifyCase3((PlaceholderType) lhsType, (SuperType) rhsType, (byte)0, fc));
+					result.get(2).add(unifyCase3((PlaceholderType) lhsType, (SuperType) rhsType, pair.getVariance(), fc));
 				}
 				else {
 					Set<UnifyPair> s1 = new HashSet<>();
@@ -659,7 +660,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 				if (first) { //writeLog(pair.toString()+"\n");
 					if (rhsType.getName().equals("A")) 
 						System.out.println();
-					result.get(4).add(unifyCase5(lhsType, (PlaceholderType) rhsType, (byte)-1, fc));
+					result.get(4).add(unifyCase5(lhsType, (PlaceholderType) rhsType, pair.getVariance(), fc));
 				}
 				else {
 					Set<UnifyPair> s1 = new HashSet<>();
@@ -683,7 +684,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 			else if(pairOp == PairOperator.SMALLERDOTWC && rhsType instanceof PlaceholderType)
 				if (first) { //writeLog(pair.toString()+"\n");
 					result.get(7).add(
-							unifyCase8(lhsType, (PlaceholderType) rhsType, (byte)0, fc));
+							unifyCase8(lhsType, (PlaceholderType) rhsType, pair.getVariance(), fc));
 				}
 				else {
 					Set<UnifyPair> s1 = new HashSet<>();
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/OrderingUnifyPair.java b/src/de/dhbwstuttgart/typeinference/unify/model/OrderingUnifyPair.java
index 55576bf0..12943305 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/OrderingUnifyPair.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/OrderingUnifyPair.java
@@ -67,6 +67,11 @@ public class OrderingUnifyPair extends Ordering<Set<UnifyPair>> {
 		}	
 	}
 	
+	/* TODO muss noch verifiziert werden PL 2018-03-21
+	 * (non-Javadoc)
+	 * fuehrt zu Fehlern bei Arrays.sort (contract nicht erfuellt)
+	 * @see com.google.common.collect.Ordering#compare(java.lang.Object, java.lang.Object)
+	 */
 	public int compare (Set<UnifyPair> left, Set<UnifyPair> right) {
 		Set<UnifyPair> lefteq = left.stream()
 				.filter(x -> (x.getLhsType() instanceof PlaceholderType && x.getPairOp() == PairOperator.EQUALSDOT))
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
index b5bf13fa..780d05a5 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
@@ -26,6 +26,13 @@ public class UnifyPair {
 	 */
 	private PairOperator pairOp;
 	
+	/**
+     * variance shows the variance of the pair
+     * -1: contravariant
+     * 1 covariant
+     * 0 invariant
+     * PL 2018-03-21
+     */
     private byte variance = 0;
     
     private boolean undefinedPair = false;
@@ -129,7 +136,7 @@ public class UnifyPair {
 	
 	@Override
 	public String toString() {
-		return "(" + lhs + " " + pairOp + " " + rhs + ")";
+		return "(" + lhs + " " + pairOp + " " + rhs + ", " + variance + ")";
 	}
 
 	/*