Setting a string value in a Checkbox using OnCheckedChangedListener returns a null value in Android

I have a Checkbox that sets a String's value when the Checkbox is checked or not checked. But my String is returning a null value. I have declared the string inside the Public class of the Activity. Why is it returning null?

I want the strings to be inserted to a database FYI.

    Lab                        = (CheckBox)findViewById(R.id.LabCheck);
    Lec                        = (CheckBox)findViewById(R.id.RoomCheck);

    Lab.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener()
    {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b)
        {
            if(b)
            {
                LabText = "withlab";

            }
            else
            {
                LabText = "without";
            }
        }
    });

    Lec.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener()
    {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b)
        {
            if (b)
            {
                LecText = "corner";
            }

            else
            {
                LecText = "notcorner";
            }
        }
    });

    Toast toast2 = Toast.makeText(getApplicationContext(), LecText, Toast.LENGTH_SHORT);
        toast2.show();
    Toast toast2 = Toast.makeText(getApplicationContext(), LabText, Toast.LENGTH_SHORT);
        toast2.show();