If you are looking to download java source code then this links will help you :

Download Java Source Code for JDK 10

https://download.java.net/openjdk/jdk10/ri/openjdk-10_src.zip

Download Java Source Code for JDK 9

https://download.java.net/openjdk/jdk9/ri/openjdk-9_src.zip

Download Java source code for JDK 8

https://download.java.net/openjdk/jdk8u40/ri/openjdk-8u40-src-b25-10_feb_2015.zip