Checkbox in the popupMenu

I have popupMenu and CheckBox. I need make write status CheckBox to boolean. This code not working:

MenuItem fast_result;
boolean fast=false;
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    switch (id) {
            case R.id.FastResult:
                fast_result = item.getSubMenu().getItem(R.id.FastResult);//This is 182 line
                fast_result.setChecked(!fast_result.isChecked());
                fast=fast_result.isChecked();
                return true;
    }
}

It is errors:

FATAL EXCEPTION: main java.lang.NullPointerException at com.alexvsalex.HelpforMath.RootsActivity.onOptionsItemSelected(RootsActivity.java:182) at android.app.Activity.onMenuItemSelected(Activity.java:2502) at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:950) at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735) at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149) at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874) at com.android.internal.view.menu.ListMenuPresenter.onItemClick(ListMenuPresenter.java:163) at android.widget.AdapterView.performItemClick(AdapterView.java:292) at android.widget.AbsListView.performItemClick(AbsListView.java:1058) at android.widget.AbsListView$PerformClick.run(AbsListView.java:2514) at android.widget.AbsListView$1.run(AbsListView.java:3168) at android.os.Handler.handleCallback(Handler.java:605) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4424) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) at dalvik.system.NativeStart.main(Native Method)

What to do?