This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Linux certifications are mainly for sysadmins. There's no Linux certification I know of that addresses Linux programming, in part because relatively little programming is Linux-specific, especially in Java.
An IDE is no substitute for an Intelligent Developer.