diff --git a/src/main/java/de/dhbwstuttgart/inferWildcards/ConstraintsGenerationUtils.java b/src/main/java/de/dhbwstuttgart/inferWildcards/ConstraintsGenerationUtils.java
index a33b2759..08c042c2 100644
--- a/src/main/java/de/dhbwstuttgart/inferWildcards/ConstraintsGenerationUtils.java
+++ b/src/main/java/de/dhbwstuttgart/inferWildcards/ConstraintsGenerationUtils.java
@@ -2,6 +2,7 @@ package de.dhbwstuttgart.inferWildcards;
 
 import java.util.HashSet;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Set;
 
 import de.dhbwstuttgart.parser.NullToken;
@@ -55,12 +56,27 @@ public final class ConstraintsGenerationUtils
 	 */
 	public static ConstraintSet<Pair> generateConstraints (
 			Map<? extends TypePlaceholder, ? extends RefTypeOrTPHOrWildcardOrGeneric> tphMap) {
-		ConstraintSet<Pair> constraintSet = new ConstraintSet<>();
-		tphMap.forEach( (tph, refType) -> {
-			ConstraintSet<Pair> constraintSet2 = generateConstraints(refType, tph);
-			constraintSet.addAll(constraintSet2);
-		});
-		return constraintSet;
+		return tphMap.entrySet().stream().map(ConstraintsGenerationUtils::generateConstraints)
+				.reduce(
+				new ConstraintSet<>(),
+				(cs, c) -> {
+					cs.addAll(c);
+					return cs;
+						});
+	}
+
+	/**
+	 * Generate the constraints for a single RefType type placeholder pair to infer
+	 * the wildcards for the generic parameter type.
+	 * 
+	 * @param tphEntry {@link Entry} of {@link TypePlaceholder} and
+	 *                 {@link RefTypeOrTPHOrWildcardOrGeneric}
+	 * @return {@link ConstraintSet} of {@link Pair} generated containing the
+	 *         constraints.
+	 */
+	private static ConstraintSet<Pair> generateConstraints (
+			Map.Entry<? extends TypePlaceholder, ? extends RefTypeOrTPHOrWildcardOrGeneric> tphEntry) {
+		return generateConstraints(tphEntry.getValue(), tphEntry.getKey());
 	}
 
 	/**