diff --git a/java/src/main/java/org/msgpack/Packer.java b/java/src/main/java/org/msgpack/Packer.java
index 3fa421ff..a92d2b68 100644
--- a/java/src/main/java/org/msgpack/Packer.java
+++ b/java/src/main/java/org/msgpack/Packer.java
@@ -23,6 +23,22 @@ import java.nio.ByteBuffer;
 import java.util.List;
 import java.util.Map;
 
+/**
+ * Packer enables you to serialize objects into OutputStream.
+ *
+ * <pre>
+ * // create a packer with output stream
+ * Packer pk = new Packer(System.out);
+ *
+ * // store an object with pack() method.
+ * pk.pack(1);
+ *
+ * // you can store String, List, Map, byte[] and primitive types.
+ * pk.pack(new ArrayList());
+ * </pre>
+ *
+ * You can serialize objects that implements {@link MessagePackable} interface.
+ */
 public class Packer {
 	protected byte[] castBytes = new byte[9];
 	protected ByteBuffer castBuffer = ByteBuffer.wrap(castBytes);
diff --git a/java/src/main/java/org/msgpack/Unpacker.java b/java/src/main/java/org/msgpack/Unpacker.java
index e84aff99..39bd8fa6 100644
--- a/java/src/main/java/org/msgpack/Unpacker.java
+++ b/java/src/main/java/org/msgpack/Unpacker.java
@@ -24,11 +24,13 @@ import java.util.Iterator;
 import java.nio.ByteBuffer;
 
 /**
- * Deserializer class that includes Buffered API, Unbuffered API,
- * Schema API and Direct Conversion API.
+ * Unpacker enables you to deserialize objects from stream.
+ *
+ * Unpacker provides Buffered API, Unbuffered API, Schema API
+ * and Direct Conversion API.
  *
  * Buffered API uses the internal buffer of the Unpacker.
- * Following code uses Buffered API with an input stream:
+ * Following code uses Buffered API with an InputStream:
  * <pre>
  * // create an unpacker with input stream
  * Unpacker pac = new Unpacker(System.in);
diff --git a/java/src/main/java/org/msgpack/package-info.java b/java/src/main/java/org/msgpack/package-info.java
new file mode 100644
index 00000000..7e9b8a27
--- /dev/null
+++ b/java/src/main/java/org/msgpack/package-info.java
@@ -0,0 +1,8 @@
+/**
+ * MessagePack is a binary-based efficient object serialization library.
+ * It enables to exchange structured objects between many languages like JSON.
+ * But unlike JSON, it is very fast and small.
+ *
+ * Use {@link Packer} to serialize and {@link Unpacker} to deserialize.
+ */
+package org.msgpack;