getting this Exception

[ghost]

I am getting this errors
java.lang.RuntimeException: Unable to start activity ComponentInfo{taskscheduler.com/taskscheduler.com.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.Toolbar cannot be cast to android.widget.Toolbar
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442)
at android.app.ActivityThread.access$800(ActivityThread.java:156)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351)
Application terminated.