Java 5 and Java 8 were both very big - generics in 5, lambdas in 8. 6 and 7 were iterative in comparison.

There were very many important changes in the meantime over that timeframe, but generics and lambdas fundamentally changed how you use the language - Java 4 is not the same language as 5, same between 7 and 8. This is not the case for the 6 and 7 releases.