I use Java extensively for my personal work and never use Gradle/Maven/Ant. I run Python scripts that marshal javac and java calls, it works great. I do cute tab completion tricks that examine the class layout and extend based on what it finds. I even have a "SmartCompJava" script that finds .java files that have newer modtimes than their corresponding .class files and just compiles them - a bit dangerous if you're not careful, but it's super-fast!