+ made SequentialExecutor a functional interface using default method

pom.xml

@@ -27,7 +27,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>io.github.q3769</groupId>
     <artifactId>conseq4j</artifactId>
-    <version>20230922.20230924.20240515</version>
+    <version>20230922.20230924.20240516</version>
     <packaging>jar</packaging>
     <name>conseq4j</name>
     <description>A Java concurrent API to sequence related tasks while concurring unrelated ones</description>

src/main/java/conseq4j/execute/ConseqExecutor.java

@@ -30,13 +30,7 @@
 import conseq4j.Terminable;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.Callable;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
+import java.util.concurrent.*;
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.ThreadSafe;
 import lombok.NonNull;
@@ -93,17 +87,6 @@ private static ConditionFactory await() {
         return Awaitility.await().forever();
     }
 
-    /**
-     * @param command the command to run asynchronously in proper sequence
-     * @param sequenceKey the key under which this task should be sequenced
-     * @return future result of the command, not downcast-able from the basic {@link Future} interface.
-     * @see ConseqExecutor#submit(Callable, Object)
-     */
-    @Override
-    public @NonNull Future<Void> execute(@NonNull Runnable command, @NonNull Object sequenceKey) {
-        return submit(Executors.callable(command, null), sequenceKey);
-    }
-
     /**
      * Tasks of different sequence keys execute in parallel, pending thread availability from the backing
      * {@link #workerExecutorService}.

src/main/java/conseq4j/execute/SequentialExecutor.java

@@ -25,6 +25,7 @@
 package conseq4j.execute;
 
 import java.util.concurrent.Callable;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 
 /**
@@ -48,8 +49,9 @@ public interface SequentialExecutor {
      * @param sequenceKey the key under which all tasks are executed sequentially
      * @return future holding run status of the submitted command
      */
-    Future<Void> execute(Runnable command, Object sequenceKey);
-
+    default Future<Void> execute(Runnable command, Object sequenceKey) {
+        return submit(Executors.callable(command, null), sequenceKey);
+    }
     /**
      * @param task the Callable task to run sequentially with others under the same sequence key
      * @param sequenceKey the key under which all tasks are executed sequentially