public static void daysTest() {
        String[] days1 = { "Sunday", "Monday", "Tuesday", "Wednesday",
                "Thursday", "Friday", "Saturday" };
        String[] days2 = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
        String[] days3 = { "U", "M", "T", "W", "R", "F", "S" };

        DualMap<String, String> testdm = new DualHashMap<String, String>();

        for (int i = 0; i < days1.length; i++) {
            testdm.put(days1[i], days2[i]);
            testdm.put(days2[i], days3[i]);
        }

        // This should print:
        // U M T W R F S
        for (String s : days2) {
            System.out.print(testdm.get(s) + " ");
        }
        System.out.println();

        // This should print:
        // Sunday Monday Tuesday Wednesday Thursday Friday Saturday
        for (String s : days2) {
            System.out.print(testdm.reverseGet(s) + " ");
        }
        System.out.println();

        for (int i = 0; i < days1.length; i++) {
            testdm.put(days1[i], days3[i]);
        }

        // This should print:
        // null null null null null null null
        for (String s : days2) {
            System.out.print(testdm.get(s) + " ");
        }
        System.out.println();

        // This should print:
        // null null null null null null null
        for (String s : days2) {
            System.out.print(testdm.reverseGet(s) + " ");
        }
        System.out.println();

        // This should print:
        // U M T W R F S
        for (String s : days1) {
            System.out.print(testdm.get(s) + " ");
        }
        System.out.println();

        // This should print:
        // Sunday Monday Tuesday Wednesday Thursday Friday Saturday
        for (String s : days3) {
            System.out.print(testdm.reverseGet(s) + " ");
        }
        System.out.println();

    }