I need to integrate some code with extensive usage of Java lambda functions.
Several restrictions I have demand that I develop my project using Eclipse Mars, with the latest ADT plugin, and not Android Studio.
The problem is that using Lambda functions demands using 1.8 JDK compliance, but if set so, I get this message:
Android requires compiler compliance level 5.0 or 6.0. Found '1.8' instead.
As @dhke said, there's no support for Java 8 on Android yet.
But you can still use JDK 8 to develop Android application. You just need to set source compatibility to either 6 or 7 depends on your
minSDKVersion. Thus, you would lose any new features introduced in Java 8, like lambda in your case.
Since you have extensive usage of lambda, Retrolambda might be an option for you. It provides backport of lambda for pre-Java 8 versions. It has Maven/Gradle/command line plugin to enable the support.
If you need other Java 8 features, AFAIK, ThreeTen ABP provides backport support for Java 8 Date Time API.