Java Reference
In-Depth Information
Table 1.1
CLDC 1.1 Packages
Package
Description
java.io
Basic classes for I/O via data streams, Read-
ers and Writers
Reduced math library, threads and system
functionality, fundamental type classes
java.lang
Support for weak references which allows
you to hold a reference to an object even
though it is garbage collected
java.lang.ref
The Vector and Hashtable classes, basic
date and calendar functionality and a
pseudo random number generator which
is great for games
java.util
CLDC specific interfaces and factories for
datagrams, connection stream etc. Imple-
mentation deferred to profiles.
javax.microedition.io
So far there have been two versions of the CLDC,
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the latest being
CLDC 1.1. Most mobile phones shipped since 2003 contain version 1.1
of the CLDC. CLDC 1.1 (see Table 1.1) includes, amongst other updates,
support for floating-point operations with the introduction of the
Float
and
Double
classes, thread naming and interrupts. The total minimum
memory requirement was also lifted from 160 KB to 192 KB.
While the discussion so far has focused on mobile phones, the CLDC
is not just for phones. As we'll see in the following section, it forms the
foundation for a number of profiles that target completely different device
families.
1.5.2 Profiles
Profiles sit on top of a configuration and allow it to be adapted and
specialized for a particular class of devices in a vertical market such
as mobile phones. A profile effectively defines a contract between an
application and a set of devices of the same type, usually by including
class libraries that are far more domain-specific than those available in
any particular configuration.
Figure 1.5 shows the three profiles that currently extend the CLDC. The
Mobile Information Device Profile (MIDP) is most relevant to our work
here; the Information Module Profile
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(IMP) targets small devices that
may have no user interface at all, such as parking meters, call boxes, and
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See the white paper at
java.sun.com/j2me/docs/pdf/CLDC-HI whitepaper-February
2005.pdf
.
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java.sun.com/products/imp/index.jsp
