Java Reference
In-Depth Information
Due to processor and power constraints, CLDC 1.0 did not support floating-point
mathematics; CLDC 1.0 devices could only perform integer math. This changed with
the advent of CLDC 1.1, as CLDC 1.1 devices must support floating-point operations.
However, as a developer, you should be aware that floating-point mathematics remains
computationally expensive. Be careful when choosing to use them, as they can cause
performance issues within your applications.
Introducing the Connected Device Configuration
The CDC is for devices that are more capable than those used by the CLDC, such as
high-end PDAs, set-top boxes, and other Internet appliances. As such, the goals of the
CDC are slightly different than those of the CLDC. Instead of targeting the largest possi-
ble number of low-cost hardware, the CDC focuses on leveraging developer and
technology skills from the existing Java SE platform while respecting the needs of
resource-constrained devices.
Unlike the CLDC, the CDC virtual machine meets the same requirements as the JVM
that powers Java SE. In fact, if you add to the CDC the profile and packages usually found
on a media-capable device, you'll find little that distinguishes the environment from a
Java SE platform except the
extra
APIs that additional packages may provide. This is the
strength of Java, and especially the more robust CDC: you can leverage your Java skills
across the entire product family line. In addition, the CDC includes all of the Java lan-
guage APIs required of the CLDC, including the GCF.
Packages containing classes defined by the CDC include
java.lang
,
java.io
,
java.net
,
java.security
,
java.text
, and
java.util
. Devices running the CDC must also support
CLDC APIs and packages; this enables the fullest possible support for all Java applica-
tions. While such devices are rare on the market today, it's an obvious future direction for
Java, as the majority of devices continue to become more and more powerful.
Understanding Profiles
Profiles collect essential APIs for building the most fundamental of applications across
a family of devices. The most well known profile by far is the MIDP, which powers
mobile phones and sits atop the CLDC. Equally important is the Foundation Profile,
which is analogous to the MIDP for providing application support classes. Unlike
CLDC-based devices, however, CDC-based devices typically also include either the
Personal Basis Profile or the Personal Profile, or both, to provide user-interface support
for applications.
