Without further ado, let's get you set up with the pieces and parts necessary to build an Android app.
The instructions presented here are accurate as of the time of this writing. However, the tools change rapidly, so these instructions may be out of date by the time you read this. Please refer to the Android Developers web site for current instructions, using this as a base guideline of what to expect.
When you write Android applications, you typically write them in Java source code. That Java source code is then turned into the stuff that Android actually runs (Dalvik bytecode in an Android package [APK] file).
Hence, the first thing you need to do is get set up with a Java development environment ...