Dates and Times - Beginning Java 8 Fundamentals - page 473

Interoperability with Legacy Datetime Classes
The legacy datetime classes have been around for over 18 years. The new Date-Time API is not going to replace them
overnight. As a Java developer, you will be tasked to maintain applications that use the legacy classes. Java 8 provides
interoperability between the legacy classes and the new Date-Time API. New methods have been added to the legacy
classes to convert their objects to the new Date-Time classes and vice versa. Interoperability of the following legacy
classes will be discussed in this section:

java.util.Date •

java.util.Calendar •

java.util.GregorianCalendar

•

java.util.TimeZone •

java.sql.Date •

java.sql.Time •

java.sql.Timestamp •

java.nio.file.attribute.FileTime

•

Table 12-7 contains the list of legacy datetime classes and their new Date-Time counterparts. All legacy classes,
except the Calendar class, provides two-way conversion. The toXxx() methods are instance methods. They return an
object of the new datetime class. The other methods are static methods, which accept an object of the new datetime
class and return an object of the legacy class. For example, the from() method in the java.util.Date class is a static
method, which takes an Instant argument and returns a java.util.Date . The toInstant() method is an instance
method and converts a java.util.Date into an Instant .

Table 12-7. Conversion Between New Datetime and Legacy Datetime Classes

Legacy Class New Methods in Legacy Class Equivalent New Datetime Class

java.util.Date from(), toInstant() Instant

Calendar toInstant() None

GregorianCalendar from(), toZonedDateTime() ZonedDateTime

TimeZone getTimeZone(), toZoneId() ZoneId

java.sql.Date valueOf(), toLocalDate() LocalDate

Time valueOf(), toLocalTime() LocalTime

Timestamp from(), toInstant() Instant

valueOf(), toLocalDateTime() LocalDateTime

FileTime from(), toInstant() Instant

Listing 12-29 shows how to convert a Date to an Instant and vice versa.