Apply suggestions from @kske 1

client/src/main/java/envoy/client/data/commands/Callable.java

@@ -0,0 +1,39 @@
+package envoy.client.data.commands;
+
+import java.util.List;
+
+/**
+ * This interface defines an action that should be performed when a system
+ * command gets called.
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+public interface Callable {
+
+	/**
+	 * Performs the instance specific action when a {@link SystemCommand} has been
+	 * called.
+	 *
+	 * @param arguments the arguments that should be passed to the
+	 *                  {@link SystemCommand}
+	 * @since Envoy Client v0.2-beta
+	 */
+	void call(List<String> arguments);
+
+	/**
+	 * Performs the instance specific action when a {@link SystemCommand} has been
+	 * called and additionally enables the user to execute his own action once it
+	 * has been called.
+	 *
+	 * @param arguments        the arguments that should be passed to the
+	 *                         {@link SystemCommand}
+	 * @param additionalAction the action to perform when this system command has
+	 *                         been called
+	 * @since Envoy Client v0.2-beta
+	 */
+	default void call(List<String> arguments, Runnable additionalAction) {
+		call(arguments);
+		additionalAction.run();
+	}
+}

client/src/main/java/envoy/client/data/commands/OnCall.java

@@ -1,30 +0,0 @@
-package envoy.client.data.commands;
-
-import java.util.function.Supplier;
-
-/**
- * This interface defines an action that should be performed when a system
- * command gets called.
- *
- * @author Leon Hofmeister
- * @since Envoy Client v0.2-beta
- */
-public interface OnCall {
-
-	/**
-	 * Performs class specific actions when a {@link SystemCommand} has been called.
-	 *
-	 * @since Envoy Client v0.2-beta
-	 */
-	void onCall();
-
-	/**
-	 * Performs actions that can only be performed by classes that are not
-	 * {@link SystemCommand}s when a SystemCommand has been called.
-	 *
-	 * @param consumer the action to perform when this {@link SystemCommand} has
-	 *                 been called
-	 * @since Envoy Client v0.2-beta
-	 */
-	void onCall(Supplier<Void> consumer);
-}

client/src/main/java/envoy/client/data/commands/SystemCommand.java

@@ -1,7 +1,7 @@
 package envoy.client.data.commands;
 
 import java.util.*;
-import java.util.function.*;
+import java.util.function.Consumer;
 
 /**
  * This class is the base class of all {@code SystemCommands} and contains an
@@ -17,7 +17,7 @@ import java.util.function.*;
  * @author Leon Hofmeister
  * @since Envoy Client v0.2-beta
  */
-public final class SystemCommand implements OnCall {
+public final class SystemCommand implements Callable {
 
 	protected int relevance;
 
@@ -55,12 +55,6 @@ public final class SystemCommand implements OnCall {
 		this.description		= description;
 	}
 
-	/**
-	 * @return the action that should be performed
-	 * @since Envoy Client v0.2-beta
-	 */
-	public Consumer<List<String>> getAction() { return action; }
-
 	/**
 	 * @return the argument count of the command
 	 * @since Envoy Client v0.2-beta
@@ -85,20 +79,10 @@ public final class SystemCommand implements OnCall {
 	 */
 	public void setRelevance(int relevance) { this.relevance = relevance; }
 
-	/**
-	 * Increments the relevance of this {@code SystemCommand}.
-	 */
 	@Override
-	public void onCall() { relevance++; }
-
-	/**
-	 * Increments the relevance of this {@code SystemCommand} and executes the
-	 * supplier.
-	 */
-	@Override
-	public void onCall(Supplier<Void> consumer) {
-		onCall();
-		consumer.get();
+	public void call(List<String> arguments) {
+		action.accept(arguments);
+		++relevance;
 	}
 
 	/**

client/src/main/java/envoy/client/data/commands/SystemCommandMap.java

@@ -155,14 +155,7 @@ public final class SystemCommandMap {
 			final var arguments = extractArguments(input, systemCommand);
 			// Executing the function
 			try {
-				systemCommand.getAction().accept(arguments);
-				systemCommand.onCall();
-			} catch (final IndexOutOfBoundsException e) {
-				logger.log(Level.SEVERE,
-						String.format(
-								"System command %s threw an IndexOutOfBoundsException. The most likely cause is a lower number of arguments than expected. It could also be a problem of the action performed: ",
-								command),
-						e);
+				systemCommand.call(arguments);
 			} catch (final NumberFormatException e) {
 				logger.log(Level.INFO,
 						String.format(