diff --git a/command/src/main/java/com/iluwatar/command/Command.java b/command/src/main/java/com/iluwatar/command/Command.java
index 85deff74e..df91e1df3 100644
--- a/command/src/main/java/com/iluwatar/command/Command.java
+++ b/command/src/main/java/com/iluwatar/command/Command.java
@@ -26,15 +26,14 @@ package com.iluwatar.command;
 /**
  * Interface for Commands.
  */
-public abstract class Command {
+public interface Command {
 
-  public abstract void execute(Target target);
+  public void execute(Target target);
 
-  public abstract void undo();
+  public void undo();
 
-  public abstract void redo();
+  public void redo();
 
-  @Override
-  public abstract String toString();
+  public String toString();
 
 }
diff --git a/command/src/main/java/com/iluwatar/command/InvisibilitySpell.java b/command/src/main/java/com/iluwatar/command/InvisibilitySpell.java
index 3e0f7bbf4..33e053cc2 100644
--- a/command/src/main/java/com/iluwatar/command/InvisibilitySpell.java
+++ b/command/src/main/java/com/iluwatar/command/InvisibilitySpell.java
@@ -26,7 +26,7 @@ package com.iluwatar.command;
 /**
  * InvisibilitySpell is a concrete command.
  */
-public class InvisibilitySpell extends Command {
+public class InvisibilitySpell implements Command {
 
   private Target target;
 
diff --git a/command/src/main/java/com/iluwatar/command/ShrinkSpell.java b/command/src/main/java/com/iluwatar/command/ShrinkSpell.java
index 87497bb7b..3f21fc7c1 100644
--- a/command/src/main/java/com/iluwatar/command/ShrinkSpell.java
+++ b/command/src/main/java/com/iluwatar/command/ShrinkSpell.java
@@ -26,7 +26,7 @@ package com.iluwatar.command;
 /**
  * ShrinkSpell is a concrete command.
  */
-public class ShrinkSpell extends Command {
+public class ShrinkSpell implements Command {
 
   private Size oldSize;
   private Target target;