update doc

Author: oldratlee

library/README.md

@@ -166,19 +166,19 @@ content = m2.getResponseBodyAsString();
 经过测试的`JDK`
 ----------------------------------
 
-JDK | 系统 | On
---- | ---- | ---
-openjdk6 64-Bit | Linux | travis-ci
-oraclejdk7 64-Bit | Linux | travis-ci
-openjdk7 64-Bit | Linux | travis-ci
-oraclejdk8 64-Bit | Linux | travis-ci
-Mac自带的jdk6 64-Bit | Mac | 个人Mac
-oraclejdk7 64-Bit | Mac | 个人Mac
-oraclejdk8 64-Bit | Mac | 个人Mac
-oraclejdk7 64-Bit | windows server 2012 r2 | appveyor
-oraclejdk7 32-Bit | windows server 2012 r2 | appveyor
-oraclejdk8 64-Bit | windows server 2012 r2 | appveyor
-oraclejdk8 32-Bit | windows server 2012 r2 | appveyor
+JDK | 系统 | On | 备注
+--- | --- | --- | ----
+openjdk6 64-Bit | Linux | travis-ci |
+oraclejdk7 64-Bit | Linux | travis-ci |
+openjdk7 64-Bit | Linux | travis-ci |
+oraclejdk8 64-Bit | Linux | travis-ci |
+applejdk6 64-Bit | Mac | 个人Mac | [jdk6及以下，Apple提供了自己的Java版本](https://java.com/zh_CN/download/faq/java_mac.xml)。
+oraclejdk7 64-Bit | Mac | 个人Mac | 从jdk7开始，Mac jdk直接在`Oracle`下载。
+oraclejdk8 64-Bit | Mac | 个人Mac |
+oraclejdk7 64-Bit | windows server 2012 r2 | appveyor |
+oraclejdk7 32-Bit | windows server 2012 r2 | appveyor |
+oraclejdk8 64-Bit | windows server 2012 r2 | appveyor |
+oraclejdk8 32-Bit | windows server 2012 r2 | appveyor |
 
 PS：  
 感谢 [travis-ci](https://travis-ci.org/) 和 [appveyor](https://ci.appveyor.com) 免费提供持续集成环境。