Well, you just lost your source code! Yikes!
WARNING: Androchef will give you a trial, it's not free :(
This guide will guide you through the process of decompiling a Java application, let's go!
Step 1: Get Androchef
First, download Androchef from http://www.neshkov.com/ac_decompiler.html
Then, run the setup and install it. This should be very easy.
Step 2: Start Decompiling
You're done! Let's start decompiling!
Select your jar file or APK to decompile and decompile it!
To build your source code, use eclipse!