diff --git a/src/seedu/addressbook/commands/Command.java b/src/seedu/addressbook/commands/Command.java
index a54cbcb5b..8f3d26e42 100644
--- a/src/seedu/addressbook/commands/Command.java
+++ b/src/seedu/addressbook/commands/Command.java
@@ -38,10 +38,9 @@ public static String getMessageForPersonListShownSummary(List<? extends ReadOnly
 
     /**
      * Executes the command and returns the result.
+     * This is an abstract method, should override in subclasses.
      */
-    public CommandResult execute(){
-        throw new UnsupportedOperationException("This method should be implement in child classes");
-    }
+    public abstract CommandResult execute();
 
     //Note: it is better to make the execute() method abstract, by replacing the above method with the line below:
     //public abstract CommandResult execute();