java SE 8 API文档：
http://www.oracle.com/technetwork/java/javase/documentation/jdk8-doc-downloads-2133158.html

jdk-8-apidocs  在线版：
http://docs.oracle.com/javase/8/docs/api/index.html

java SE 7 API文档：

http://www.oracle.com/technetwork/java/javase/documentation/java-se-7-doc-download-435117.html

java SE 6 API文档：

http://www.oracle.com/technetwork/java/javase/downloads/jdk-6u25-doc-download-355137.html

Java Platform Standard Edition 8 Documentation
http://docs.oracle.com/javase/8/docs/