Q:

Multiple entries with same key: 24.0.0 rc4=24.0.0 rc4

After upgrade Android Studio to 2.2.3 it shows an error with:

IllegalArgumentException: Multiple entries with same key: 24.0.0
  rc4=24.0.0 rc4 and 24.0.0 rc4=24.0.0 rc4

A:

Had this occur recently after updating a few bits.
My solution was to open the Preferences in Android Studio, browse to Android SDK -> SDK Tools, you will most likely see multiple copies of 24.0.0 rc4 (one with a dash instead of a space in the version name) under Android SDK Build-Tools. Uninstall both copies by unchecking them, and then hitting Apply. Once uninstalled, the list should go back to showing only one 24.0.0 version called 24-rc4, install this and resync Gradle.
It might also help to change the buildToolsVersion in your Gradle files to 24-rc4. 

A:

Just go to folder ANDROID_SDK_LOCATION/build-tools and delete 24.0.0-preview (or another folders)
Or of course you can go over Android SDK Manager / Android Studio > SDK Manager > SDK Tools > Show Package Details and uncheck preview and older RC versions. This make the same action as just delete build-tools/24... folder.

