Unable to establish connection to adb : Android Studio Error

While working with Android Studio 1.0.2 (on my Mac OS X 10.10 Operating system) I got the following error!

Unable to establish a connection to ADB.

If this happens, run 'adb devices -l' from the command line and see if it lists your devices. If ADB from the command line works, then please file a bug at http://b.android.com, including the output of the 'adb devices -l' command and your idea.log file (Help | Show Log in Files)

Solution :

You need to kill the ADB process that is running, to do so,

1. Go to Spotlight search, open Activity Monitor,

2. Loop for ADB under CPU tag,

3. Now Select it and Force Quit the process.

⚡️ You can kill ADB process through Terminal command too, by simply typing Kill -9 adb