Errors

 java.lang.RuntimeException: Unable to start activity ComponentInfo{infinitetech.studenthelper/infinitetech.studenthelper.MainActivity}: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.support.v7.widget.Toolbar
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2198)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2225)
            at android.app.ActivityThread.access$600(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1301)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5096)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
            at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.support.v7.widget.Toolbar
            at infinitetech.studenthelper.MainActivity.onCreate(MainActivity.java:21)
            at android.app.Activity.performCreate(Activity.java:5244)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2225)
            at android.app.ActivityThread.access$600(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1301)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5096)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
            at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
            at dalvik.system.NativeStart.main(Native Method)
01-28 17:21:00.805  26339-26341/infinitetech.studenthelper D/dalvikvm﹕ GC_CONCURRENT freed 258K, 5% free 9554K/10055K, paused 16ms+4ms, total 83ms
01-28 17:21:00.805  26339-26339/infinitetech.studenthelper D/dalvikvm﹕ WAIT_FOR_CONCURRENT_GC blocked 18ms