Java如何将文本字符串解析为日期和时间？
在此代码段例子中，你将学会如何解析文本字符串成的实例LocalDate，LocalTime和LocalDateTime。所有这些类都提供了一种parse()方法，该方法接受表示有效日期和时间信息的文本字符串参数，并将其转换为相应的对象。
如果传递给该parse()方法的文本字符串未表示有效的日期或时间信息，则此方法将引发RuntimeException类型DateTimeParseException异常。如果要处理此异常，则应将代码包装在try-catch块中。
让我们以下面的代码片段为例：
package org.nhooo.example.datetime;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeParseException;
public class DateTimeParseDemo {
public static void main(String[] args) {
//将字符串“2014-09-12”解析为LocalDate实例。"2014-09-12" into LocalDate instance.
LocalDate date = LocalDate.parse("2014-09-12");
//将字符串“2014-09-12”解析为LocalDate实例。"17:51:15: into LocalTime instance.
LocalTime time = LocalTime.parse("17:51:15");
//将字符串“2014-09-12”解析为LocalDate实例。"2014-09-12T17:51:15" into LocalDateTime instance.
LocalDateTime dateTime = LocalDateTime.parse("2014-09-12T17:51:15");
System.out.println("date = " + date);
System.out.println("time = " + time);
System.out.println("dateTime = " + dateTime);
try {
//当无法解析字符串时，类型为RuntimeException
//DateTimeParseException将被抛出。
LocalDate date1 = LocalDate.parse("2014-02-31");
System.out.println("date1 = " + date1);
} catch (DateTimeParseException e) {
e.printStackTrace();
}
}
}运行此代码段将产生以下结果：
date = 2014-09-12
time = 17:51:15
dateTime = 2014-09-12T17:51:15
java.time.format.DateTimeParseException: Text '2014-02-31' could not be parsed: Invalid date 'FEBRUARY 31'
at java.time.format.DateTimeFormatter.createError(DateTimeFormatter.java:1918)
at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1853)
at java.time.LocalDate.parse(LocalDate.java:400)
at java.time.LocalDate.parse(LocalDate.java:385)
at org.nhooo.example.datetime.DateTimeParseDemo.main(DateTimeParseDemo.java:35)
Caused by: java.time.DateTimeException: Invalid date 'FEBRUARY 31'
at java.time.LocalDate.create(LocalDate.java:431)
at java.time.LocalDate.of(LocalDate.java:269)
at java.time.chrono.IsoChronology.resolveYMD(IsoChronology.java:560)
at java.time.chrono.IsoChronology.resolveYMD(IsoChronology.java:123)
at java.time.chrono.AbstractChronology.resolveDate(AbstractChronology.java:472)
at java.time.chrono.IsoChronology.resolveDate(IsoChronology.java:492)
at java.time.chrono.IsoChronology.resolveDate(IsoChronology.java:123)
at java.time.format.Parsed.resolveDateFields(Parsed.java:351)
at java.time.format.Parsed.resolveFields(Parsed.java:257)
at java.time.format.Parsed.resolve(Parsed.java:244)
at java.time.format.DateTimeParseContext.toResolved(DateTimeParseContext.java:331)
at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1953)
at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1849)
... 3 more我们可以从上面的输出看，分析的文本字符串"2014-02-31"给我们DateTimeParseException，因为二月份的31是不是有效日期。