source not found the source attachment does not contain the source for the file thread.class.

Eclipse在查看某些类的open declaration时，报source not found   the source attachment does not contain the source for the file thread.class. you can change the source attachment by clicking change attached source below.

解决方法：下载一个jdk .注意是jdk安装包，或者免安装包。

找到一个src.rar包放到jdk目录下。然后关联一下就行了