Java Reference
In-Depth Information
The situation is somewhat simpler in CLDC/MIDP. There are fewer classes, for one thing,
and the Date class API has been cleaned up. In MIDP, the four responsibilities we just discussed
are assigned to classes as follows:
Points in time are represented by instances of java.util.Date , just like before. The Date
class, in essence, is just a wrapper for a long value that indicates the number of milliseconds
since midnight on January 1, 1970. (This is a standard way of representing time. It will
work for about another 290 million years, so don't worry about another millennium bug.)
Calendars are still represented by instances of java.util.Calendar . However, the
GregorianCalendar class is no longer part of the public API. To get a Calendar instance,
you can use the getInstance() factory method. Chances are you won't need to do this.
Formatting classes are hidden from view in MIDP. One of the user interface classes,
javax.microedition.lcdui.DateField , can convert a Date to a human-readable display,
eliminating the need for you to mess around with date formatters yourself. Essentially
DateField is a graphic wrapper around a Date instance. It also allows the user to edit
calendar and clock fields to produce a new Date value. See Chapter 6 for a full discussion
of DateField .
Time zones are still represented by instances of java.util.TimeZone . TimeZone offers
several static methods for examining the available time zones and getting an instance
representing a particular time zone.
Summary
Developers are bombarded with information, and the best developers are the ones who can
learn new material fast. Every once in a while, though, something you already know can be
used again. This is one of those cases—something you already know about, the J2SE APIs,
comes in very handy as you learn MIDP programming. MIDP's java.lang , java.io , and
java.util packages contain classes that look and act a lot like the corresponding classes in J2SE.
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