Question: After upgrading to Android Studio 2.4 Preview 4 I got this error

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> Error:Could not initialize class com.android.ide.common.util.ReadWriteProcessLock
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Answer: 
After some research, I found out it's a known bug and fortunately, the solution is very simple.

from [release notes](https://androidstudio.googleblog.com/2017/04/android-studio-24-preview-4-is-now.html):

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> After updating the Android plugin version, you need to stop the Gradle daemon to apply the update ([Issue 267099](https://code.google.com/p/android/issues/detail?id=267099)). Otherwise, Gradle sync and builds fail with the following error:
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> `Could not initialize class com.android.ide.common.util.ReadWriteProcessLock, Failed to notify build listener or java.lang.ExceptionInInitializerError.`
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> 
> To stop the daemon, you can either:
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> 1- restart Android Studio,
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> 
> or 
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> 2- enter the following command in the IDE's Terminal window: `./gradlew --stop` or for windows `gradlew --stop`
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> Gradle restarts the daemon for you the next time you sync or build your
>  project.
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> 
>
Another convenient method:

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> Android Studio -> File -> Invalidate Caches / Restart... -> Invalidate and Restart
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