Java 8 left introduced some new language features, which are far from being obvious even for expirienced Java developers.
Lambdas:
SomeCollection.compare((c1,c2)->c1.orderIndex()-c2.orderIndex());
and Streams:
SomeCollection.stream().filter(c->c.orderIndex()>100).map(c->c.orderIndex())
But if you overcome this difficulties, these features are great!