1) Download java JDK:
2) Install Java JDKd and remember the path where you Java is installed.
3) Click windows button and type "Environment Variables" and click "Edit the system Environment Variables". System Properties window will be opened. Click "Environment Variables"
4) Click "New"
5) Enter JAVA_HOME to 1st field. Go to the location, where your Java is installed. Remember that path from Java installation? Mine was C:\Program Files\Java so go this folder and you will find at least 2 folders: one with jre and another with jdk words inside the name. I found these two: jre7 and jdk1.7.0_21 so enter the path to JDK to the 2nd field, mine path is C:\Program Files\Java\jdk1.7.0_21
6) Close all boxes with "OK" or "Save" buttons.
7) Start your Android Studio ;)
Share this tutorial with others! Thank you.
BTW, if while starting Android Studio you will get an error, that some java class is not found and there is some error with path, what you have just done, then go to Environment Variables again, find your added JAVA_HOME variable and make sure, that you have entered the path to jre, not jdk ;)