As I understand, Oracle's lawsuit is because Google modified Java's source code and did not submit the changes.
This is the principle of all open source projects. If someone improves or modifies the code, must submit the changes.
Android uses the Linux kernel. If Google modifies the source code of the Linux kernel, they must submit the changes. Otherwise, Linus Torvalds is entitled to sue Google the same way Oracle did.
I am not taking side with Oracle. In fact, I am taking side with the open source community.