As per the Specjbb benchmark, JDK9 compact strings optimization itself provides,
* 21% memory footprint reduction
* 27% less GC
* 5% throughput improvments
https://www.infoq.com/presentations/java-se-9-cloud - check this presentation for more details.Impressive numbers.
Due to value types support, which are part of Java 10's roadmap.
http://benchmarksgame.alioth.debian.org/u64q/go.html