Greetings. I have a good overall understanding of Minecraft plugins such as Bukkit and Spigot APIs. I used to design plugins for my friends' server like shop manager, bank manager, and other similar stuff. I have also designed a custom game-mode for them, basically like egg wars but with more options. I have publically posted open-source projects such as bank manager and shop manager in my Github profile that I can gladly show you.
Plus, I have a decent experience at Java which exceeds 3 years of experience.