Code Smell: Remove duplicate logic for searching in sets

3-Domain/src/main/java/abstraction/CustomSetPersistenceDecorator.java

@@ -3,12 +3,15 @@ package abstraction;
 import datastructures.set.CustomSet;
 import datastructures.set.CustomStrictSet;
 
+import java.util.Optional;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 
 /**
  * A Decorator to intercept all state changes on a set and sync them with the persistence layer of the
  * application.
+ *
  * @param <T> The data type that should be stored and updated in the persistence layer
  */
 public class CustomSetPersistenceDecorator<T> implements CustomSet<T> {
@@ -22,12 +25,17 @@ public class CustomSetPersistenceDecorator<T> implements CustomSet<T> {
 	}
 
 	@Override
-	public Stream<T> stream(){
+	public Optional<T> find(Predicate<T> predicate) {
+		return set.find(predicate);
+	}
+
+	@Override
+	public Stream<T> stream() {
 		return set.stream();
 	}
 
 	@Override
-	public boolean add(T value){
+	public boolean add(T value) {
 		persistenceAdapter.add(value);
 		return set.add(value);
 	}

3-Domain/src/main/java/category/CategoryRepository.java

@@ -19,7 +19,7 @@ public class CategoryRepository {
 	}
 
 	public Optional<Category> getByName(CategoryName name) {
-		return categories.stream().filter(category -> category.getName().equals(name)).findFirst();
+		return categories.find(category -> category.getName().equals(name));
 	}
 
 	public CategoryId getIdByName(CategoryName name) {
@@ -31,7 +31,7 @@ public class CategoryRepository {
 	}
 
 	public Optional<Category> getById(CategoryId id) {
-		return categories.stream().filter(category -> category.getId().equals(id)).findFirst();
+		return categories.find(category -> category.getId().equals(id));
 	}
 
 	public Set<Category> getAll() {

3-Domain/src/main/java/link/LinkRepository.java

@@ -1,8 +1,8 @@
 package link;
 
-import datastructures.set.CustomSet;
 import abstraction.CustomSetPersistenceDecorator;
 import abstraction.PersistenceAdapter;
+import datastructures.set.CustomSet;
 import exeptions.LinkAlreadyExists;
 import exeptions.LinkDoesNotExist;
 
@@ -17,11 +17,11 @@ public class LinkRepository {
 	}
 
 	public Optional<Link> getById(LinkId id) {
-		return links.stream().filter(link -> link.getId().equals(id)).findFirst();
+		return links.find(link -> link.getId().equals(id));
 	}
 
 	public Optional<Link> getByUrl(LinkUrl url) {
-		return links.stream().filter(link -> link.getUrl().equals(url)).findFirst();
+		return links.find(link -> link.getUrl().equals(url));
 	}
 
 	public void removeById(LinkId id) {

4-Abstraction/src/main/java/datastructures/set/CustomSet.java

@@ -1,17 +1,19 @@
 package datastructures.set;
 
+import java.util.Optional;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 
 public interface CustomSet<T> {
 
-
-
 	Stream<T> stream();
 
 	boolean add(T value);
 
 	boolean remove(T value);
 
+	Optional<T> find(Predicate<T> predicate);
+
 	Set<T> getSet();
 }

4-Abstraction/src/main/java/datastructures/set/CustomStrictSet.java

@@ -1,6 +1,8 @@
 package datastructures.set;
 
+import java.util.Optional;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 
 public class CustomStrictSet<T> implements CustomSet<T> {
@@ -16,6 +18,11 @@ public class CustomStrictSet<T> implements CustomSet<T> {
 		return this.set.stream();
 	}
 
+	@Override
+	public Optional<T> find(Predicate<T> predicate) {
+		return set.stream().filter(predicate).findFirst();
+	}
+
 	@Override
 	public Set<T> getSet() {
 		return this.set;