子在川上曰

　　在SWT中還沒有日期控件，所以我的日期是用文本框手工輸入的，這時就需要驗證輸入的日期是否合法。在之前我是復制很久以前寫的一段代碼，它的解決方法是分解日期字串，然后檢查，這很笨且不嚴格。正確的方案應該是利用DateFormat類來檢查，如下所示：
 
public final class StringUtil {
    private static Calendar calendar = Calendar.getInstance();
    private static DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
    private static DateFormat dateTimeFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    static {
        dateFormat.setLenient(false);//這個的功能是不把1996-13-3 轉換為1997-1-3
        dateTimeFormat.setLenient(false);
    }
 
    public static Date parseStringToDate(String dateStr) {
        if (dateStr == null || dateStr.trim().equals(""))
            return null;
        dateStr = dateStr.trim();
        Date date = null;
        try {
            if (dateStr.length() <= 10) {
                date = dateFormat.parse(dateStr);
            } else {
                date = dateTimeFormat.parse(dateStr);
            }
        } catch (Exception e) {
            throw new IllegalArgumentException("你輸入的日期不合法，請重新輸入");
        }
        return date;
    }
}

 
這個方法的Test Case也一并給出如下：
 
public class TestStringUtil extends TestCase {
    public void testParseStringToDate() {
        {
            Calendar c = Calendar.getInstance();
            c.clear();
            c.set(2000, 1, 3, 0, 0, 0);
            Date d = StringUtil.parseStringToDate("2000-02-03");
            assertEquals(c.getTime().getTime(), d.getTime());
        }
        {
            Calendar c = Calendar.getInstance();
            c.clear();
            c.set(2000, 1, 3, 11, 22, 33);
            Date d = StringUtil.parseStringToDate("2000-02-03 11:22:33");
            assertEquals(c.getTime().getTime(), d.getTime());
        }
        {
            Calendar c = Calendar.getInstance();
            c.clear();
            c.set(2000, 1, 3, 0, 0, 0);
            Date d = StringUtil.parseStringToDate("2000-02-3");
            assertEquals(c.getTime().getTime(), d.getTime());
        }
        {
            Calendar c = Calendar.getInstance();
            c.clear();
            c.set(2000, 1, 3, 1, 2, 3);
            Date d = StringUtil.parseStringToDate("2000-02-03 1:02:03");
            assertEquals(c.getTime().getTime(), d.getTime());
        }
        {
            assertNull(StringUtil.parseStringToDate(""));
            assertNull(StringUtil.parseStringToDate("  "));
            assertNull(StringUtil.parseStringToDate(null));
        }
    }
    public void testParseStringToDateException() {
        testParseStringToDateException("2000");
        testParseStringToDateException("2000-13-03");
        testParseStringToDateException("2000-02-03 51:02:03");
        testParseStringToDateException("2000-02-03 01:f2:03");
        testParseStringToDateException("2000-02-03 01:02");
        testParseStringToDateException("2000-02-03 01:02:222");
    }
    private void testParseStringToDateException(String dateStr) {
        try {
            StringUtil.parseStringToDate(dateStr);
            fail("末拋出異常");
        } catch (Exception e) {
            assertTrue(true);
        }
    }
}