java8time.java

    public static final DateTimeFormatter TIME_PATTERN = DateTimeFormatter.ofPattern("HHmm");

    public BigDecimal getRealKosu() {
        LocalTime start = LocalTime.parse(strTime, TIME_PATTERN);
        LocalTime end = LocalTime.parse(endTime, TIME_PATTERN);
        LocalTime rest = LocalTime.parse(restTime, TIME_PATTERN);
        Duration du = Duration.between(start, end);
        Duration du2 = Duration.between(LocalTime.MIN, rest);
        Duration du3 = du.minus(du2);
        return new BigDecimal(du3.toMinutes() / 60.0);
    }