Yes, the examples are mostly C++. There are small Java snippets used to show some concepts unique to Java. I've tried to keep almost all the examples in the same language, only mentioning in the discussion the differences of the other languages.
Java is a nice language in the sense that it has much support for the parallel programming in the ready APIs. But it's also inconvenient in a book discussing how things work under the cover, exactly because these APIs are the opaque covers :-) So you can read it and get an idea of what happens inside, and see the reasons why some APIs work better in some situations and worse in the others. And how to make your own that works the way you need :-)