How to turn off Android phone programmatically?

Question

I want to make a lock screen application. When the phone is in the lock mode, it will turn off the phone while the USB is plugged for prevent other users from accessing the phone data. Does anyone know how to turn off Android devices programmatically so other people can't access the data while a device on the lock mode?

here's the code to lock the home button on the lock screen activity:

@Override
public void onAttachedToWindow()
{   
    this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);     
    super.onAttachedToWindow();  
}

Answer 1

It is impossible with the public Android SDK.

Answer 2

Yes it is possible,

Using making system application(Using firmware) not download application. You can get the code for power off android device from AOSP.