diff --git a/design-pattern/gof/src/decorator/after/App.java b/design-pattern/gof/src/decorator/after/App.java
new file mode 100644
index 00000000..f35d6a3b
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/App.java
@@ -0,0 +1,25 @@
+package decorator.after;
+
+public class App {
+
+    private static boolean enabledSpamFilter = true;
+
+    private static boolean enabledTrimming = true;
+
+    public static void main(String[] args) {
+        CommentService commentService = new DefaultCommentService();
+
+        if (enabledSpamFilter) {
+            commentService = new SpamFilteringCommentDecorator(commentService);
+        }
+
+        if (enabledTrimming) {
+            commentService = new TrimmingCommentDecorator(commentService);
+        }
+
+        Client client = new Client(commentService);
+        client.writeComment("오징어게임");
+        client.writeComment("보는게 하는거 보다 재밌을 수가 없지...");
+        client.writeComment("http://whiteship.me");
+    }
+}
diff --git a/design-pattern/gof/src/decorator/after/Client.java b/design-pattern/gof/src/decorator/after/Client.java
new file mode 100644
index 00000000..e4c5adc0
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/Client.java
@@ -0,0 +1,14 @@
+package decorator.after;
+
+public class Client {
+
+    private CommentService commentService;
+
+    public Client(CommentService commentService) {
+        this.commentService = commentService;
+    }
+
+    public void writeComment(String comment) {
+        commentService.addComment(comment);
+    }
+}
diff --git a/design-pattern/gof/src/decorator/after/CommentDecorator.java b/design-pattern/gof/src/decorator/after/CommentDecorator.java
new file mode 100644
index 00000000..ef664ef2
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/CommentDecorator.java
@@ -0,0 +1,15 @@
+package decorator.after;
+
+public class CommentDecorator implements CommentService {
+
+    private CommentService commentService;
+
+    public CommentDecorator(CommentService commentService) {
+        this.commentService = commentService;
+    }
+
+    @Override
+    public void addComment(String comment) {
+        commentService.addComment(comment);
+    }
+}
diff --git a/design-pattern/gof/src/decorator/after/CommentService.java b/design-pattern/gof/src/decorator/after/CommentService.java
new file mode 100644
index 00000000..ef3f75c9
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/CommentService.java
@@ -0,0 +1,6 @@
+package decorator.after;
+
+public interface CommentService {
+
+    void addComment(String comment);
+}
diff --git a/design-pattern/gof/src/decorator/after/DefaultCommentService.java b/design-pattern/gof/src/decorator/after/DefaultCommentService.java
new file mode 100644
index 00000000..0bc99d6e
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/DefaultCommentService.java
@@ -0,0 +1,8 @@
+package decorator.after;
+
+public class DefaultCommentService implements CommentService {
+    @Override
+    public void addComment(String comment) {
+        System.out.println(comment);
+    }
+}
diff --git a/design-pattern/gof/src/decorator/after/SpamFilteringCommentDecorator.java b/design-pattern/gof/src/decorator/after/SpamFilteringCommentDecorator.java
new file mode 100644
index 00000000..74cb5d7f
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/SpamFilteringCommentDecorator.java
@@ -0,0 +1,18 @@
+package decorator.after;
+
+public class SpamFilteringCommentDecorator extends CommentDecorator {
+    public SpamFilteringCommentDecorator(CommentService commentService) {
+        super(commentService);
+    }
+
+    @Override
+    public void addComment(String comment) {
+        if (isNotSpam(comment)) {
+            super.addComment(comment);
+        }
+    }
+
+    private boolean isNotSpam(String comment) {
+        return !comment.contains("http");
+    }
+}
diff --git a/design-pattern/gof/src/decorator/after/TrimmingCommentDecorator.java b/design-pattern/gof/src/decorator/after/TrimmingCommentDecorator.java
new file mode 100644
index 00000000..1e000087
--- /dev/null
+++ b/design-pattern/gof/src/decorator/after/TrimmingCommentDecorator.java
@@ -0,0 +1,16 @@
+package decorator.after;
+
+public class TrimmingCommentDecorator extends CommentDecorator {
+    public TrimmingCommentDecorator(CommentService commentService) {
+        super(commentService);
+    }
+
+    @Override
+    public void addComment(String comment) {
+        super.addComment(trim(comment));
+    }
+
+    private String trim(String comment) {
+        return comment.replace("...", "");
+    }
+}
diff --git a/design-pattern/gof/src/decorator/before/Client.java b/design-pattern/gof/src/decorator/before/Client.java
new file mode 100644
index 00000000..d9398272
--- /dev/null
+++ b/design-pattern/gof/src/decorator/before/Client.java
@@ -0,0 +1,22 @@
+package decorator.before;
+
+public class Client {
+
+    private CommentService commentService;
+
+    public Client(CommentService commentService) {
+        this.commentService = commentService;
+    }
+
+    private void writeComment(String comment) {
+        commentService.addComment(comment);
+    }
+
+    public static void main(String[] args) {
+        Client client = new Client(new SpamFilteringCommentService());
+        client.writeComment("오징어게임");
+        client.writeComment("보는게 하는거 보다 재밌을 수가 없지...");
+        client.writeComment("http://whiteship.me");
+    }
+
+}
diff --git a/design-pattern/gof/src/decorator/before/CommentService.java b/design-pattern/gof/src/decorator/before/CommentService.java
new file mode 100644
index 00000000..9c83d2a8
--- /dev/null
+++ b/design-pattern/gof/src/decorator/before/CommentService.java
@@ -0,0 +1,7 @@
+package decorator.before;
+
+public class CommentService {
+    public void addComment(String comment) {
+        System.out.println(comment);
+    }
+}
diff --git a/design-pattern/gof/src/decorator/before/SpamFilteringCommentService.java b/design-pattern/gof/src/decorator/before/SpamFilteringCommentService.java
new file mode 100644
index 00000000..4ddba94b
--- /dev/null
+++ b/design-pattern/gof/src/decorator/before/SpamFilteringCommentService.java
@@ -0,0 +1,16 @@
+package decorator.before;
+
+public class SpamFilteringCommentService extends CommentService {
+
+    @Override
+    public void addComment(String comment) {
+        boolean isSpam = isSpam(comment);
+        if (!isSpam) {
+            super.addComment(comment);
+        }
+    }
+
+    private boolean isSpam(String comment) {
+        return comment.contains("http");
+    }
+}
diff --git a/design-pattern/gof/src/decorator/before/TrimmingCommentService.java b/design-pattern/gof/src/decorator/before/TrimmingCommentService.java
new file mode 100644
index 00000000..cd2d15e8
--- /dev/null
+++ b/design-pattern/gof/src/decorator/before/TrimmingCommentService.java
@@ -0,0 +1,14 @@
+package decorator.before;
+
+public class TrimmingCommentService extends CommentService {
+
+    @Override
+    public void addComment(String comment) {
+        super.addComment(trim(comment));
+    }
+
+    private String trim(String comment) {
+        return comment.replace("...", "");
+    }
+
+}