android - I'm using gowong/material-sheet-fab but it's showing me errors .Can anyone help me out?

Here is my Fab Activity

public class Fab extends FloatingActionButton implements AnimatedFab {
public Fab(Context context) {
    super(context);
}
@Override
public void show() {
    show(0, 0);
}
@SuppressLint("RestrictedApi")
@Override
public void show(float translationX, float translationY) {
    setVisibility(View.VISIBLE);
}
/**
 * Hides the FAB.
 */
@SuppressLint("RestrictedApi")
@Override
public void hide() {
    setVisibility(View.INVISIBLE);
}

}

Here is my Main Activity

 // MATERIAL ANIMATED FAB
    Fab fab = findViewById(R.id.fab);
    View sheetView = findViewById(R.id.fab_sheet);
    View overlay = findViewById(R.id.overlay);
    int sheetColor = getResources().getColor(R.color.fab_sheet_color);
    int fabColor = getResources().getColor(R.color.fab_color);
    // Initialize material sheet FAB
    materialSheetFab = new MaterialSheetFab<>(fab, sheetView, overlay,
            sheetColor, fabColor);
    materialSheetFab.setEventListener(new MaterialSheetFabEventListener() {
        @Override
        public void onShowSheet() {
            // Called when the material sheet's "show" animation starts.
        }
        @Override
        public void onSheetShown() {
            // Called when the material sheet's "show" animation ends.
        }
        @Override
        public void onHideSheet() {
            // Called when the material sheet's "hide" animation starts.
        }
        public void onSheetHidden() {
            // Called when the material sheet's "hide" animation ends.
        }
    });

Here is my logcat

Process: com.teepe.teepe, PID: 29259
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.teepe.teepe/com.teepe.teepe.MainActivity}: java.lang.ClassCastException: android.support.design.widget.FloatingActionButton cannot be cast to com.teepe.teepe.Fab
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: java.lang.ClassCastException: android.support.design.widget.FloatingActionButton cannot be cast to com.teepe.teepe.Fab
at com.teepe.teepe.MainActivity.onCreate(MainActivity.java:95)
at android.app.Activity.performCreate(Activity.java:6662)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6077) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)