public int weekOfYear() {
		return getField(DateField.WEEK_OF_YEAR);
	}
@Test
	public void weekOfYearTest() {
		DateTime date = DateUtil.parse("2016-12-27");
		//noinspection ConstantConditions
		assertEquals(2016, date.year());
		//跨年的周返回的总是1
		assertEquals(1, date.weekOfYear());
	}