标签:java java-8 datetime-format java-date
在Java 8 Date Time API中,我将使用DateTimeFormatter API打印时间,如下所示:
DateTimeFormatter timeFormatter = DateTimeFormatter.ofLocalizedTime(FormatStyle.FULL);
LocalTime time = LocalTime.of(12, 45, 0);
System.out.println(timeFormatter.format(time));
FormatStyle.FULL – 此格式样式适用于LocalDate和LocalDateTime实例.但是使用LocalTime实例抛出异常:
java.time.DateTimeException: Unable to extract value: class java.time.format.DateTimePrintContext$1
根据文件:
public enum FormatStyle {
// ordered from large to small
/**
* Full text style, with the most detail.
* For example, the format might be 'Tuesday, April 12, 1952 AD' or '3:30:42pm PST'.
*/
FULL,
为什么会抛出异常?
解决方法:
看起来你受到了JDK-JDK-8085887: java.time.format.FormatStyle.LONG or FULL causes unchecked exception的攻击(在JDK 9中修复).
该例外的原因在第一条评论中说明:
Printing a time nearly always requires the timezone to be known and available.
The LocalDateTime does not have a field or value for the timezone.
评论还指出,由于模式不同,这是区域性的,但这可能与您的案例无关.不过我会把它作为参考包括在内:
The program shows different behaviors in different locales because the locale specific pattern selected may or may not include a pattern letter than prints the timezone or zone offset. Those patterns including the letters: V, z, O, X, or, x require a timezone.
在查看差异时(例如在DateTimeFormatter
中),您可以看到他们只是更新了javadoc以反映这一点(对异常消息进行了一些额外的改进):
@@ -617,10 +617,13 @@
* looking up the pattern required on demand.
* <p>
* The returned formatter has a chronology of ISO set to ensure dates in
* other calendar systems are correctly converted.
* It has no override zone and uses the {@link ResolverStyle#SMART SMART} resolver style.
+ * The {@code FULL} and {@code LONG} styles typically require a time-zone.
+ * When formatting using these styles, a {@code ZoneId} must be available,
+ * either by using {@code ZonedDateTime} or {@link DateTimeFormatter#withZone}.
*
* @param timeStyle the formatter style to obtain, not null
* @return the time formatter, not null
*/
public static DateTimeFormatter ofLocalizedTime(FormatStyle timeStyle) {
如果您向DateTimeFormatter实例添加时区,它可以毫无例外地工作:
DateTimeFormatter timeFormatter = DateTimeFormatter
.ofLocalizedTime(FormatStyle.FULL)
.withZone(ZoneId.systemDefault());
LocalTime time = LocalTime.of(12, 45, 0);
System.out.println(timeFormatter.format(time));
标签:java,java-8,datetime-format,java-date 来源: https://codeday.me/bug/20190611/1216325.html
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