Android moved to ARt from Dalvik in the version 5.0. So I was looking into performance enhancements for Java applications. I am using Genymotion and AVD emulators. Plus opensource Java Whetstone apk available from, http://www.roylongbottom.org.uk/android%20benchmarks.htm
However, I am surprised at the results. There is significant performance improvement from Android 4.4.4 to 5.0. However, there is also performance improvement from Android 4.1.1 to 4.4.4. I have searched but found nothing on what changed in Dalvik Java at 4.4.4. The 4.4.4 kitkat is running under dalvik not ART.
I have installed Android 5.01 SDK platform under Eclipse and this also shows that my Java Whetstone apk runs faster than earlier Android versions. Most significant gain was on my LinpackJava.apk. Then my JavaDraw.apk was much slower.
Eclipse was running on a Core i7 CPU via Ubuntu. It is not clear whether similar performance differences would apply using an ARM CPU.