Override toString() method in Command

Overriding the toString() method provides more human-readable feedback
when a problem occurs, including the version of the plugin if
applicable.

src/main/java/org/bukkit/command/Command.java

@@ -350,4 +350,9 @@ public abstract class Command {
             }
         }
     }
+
+    @Override
+    public String toString() {
+        return getClass().getName() + '(' + name + ')';
+    }
 }