EditText checking

I'm trying to check an EditText value, but the application crashes.
How can I handle my EditText?

        String stra_txt = edit_1.getText().toString();
        boolean first = false;
        if (stra_txt.equals("1") || stra_txt.equals("0"))
            {
                first = true;
            }
        else
            {
                first = false;
            }

        if(first = true)
            zheg();
        else
        {System.exit(0);}

this code does not work too:

        String stra_txt = edit_1.getText().toString();

        if (stra_txt.equals("1") || stra_txt.equals("0"))
            {
                zheg();
            }
        else
            {
                System.exit(0);
            }