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P800 Smartphone
White Paper, May 2002
47
J2ME CLDC/MIDP
J2ME CLDC 1.0 (Java2 Micro Edition, Connected Limited Device Configuration, version 1.0) is an
edition of Java aimed at small resource-constrained mobile devices where the runtime
environment must fit into a few hundred kilobytes of memory (as compared to the 2.5Mb required
for a typical PersonalJava environment).
MIDP (Mobile Information Device Profile) defines a programming API which has gained wide
industry acceptance, and many MIDP compliant mobile phones are anticipated to come to
market. A large number of applications for this environment is therefore to be expected.
The P800 supports this J2ME CLDC 1.0 / MIDP 1.0 environment. Applications may make use of
the following services:
• Persistent storage (RecordStore class only – no access to the rest of the filing system)
• Display – full 276 x 208 (i.e. minus the application picker and status bar)
•
Touch Screen
• Virtual Keyboard and Jog Dial (up, down, select) input
J2ME/CLDC uses a security model, often referred to as a sandbox. The sandbox includes a
number of system components working together to ensure that untrusted applications cannot gain
access to system resources.
MIDP applications can interact with arbitrary remote services that exist as a URL. Data may also
be exchanged with remote devices that accept an HTTP or datagram connection.
Applications are typically downloaded from the mobile operator’s portal or the internet.
Applications are used in FO mode. When the flip closes, the instance of the Virtual Machine is not
visible, but the user may return to the application by selecting it from the Application Launcher.
MIDP Application
running on
MIDP/CLDC/KVM
UIQ Virtual
Keyboard +
Jog Dial
Internet
Persistent
Storage
JAR file
resource
Services and
pages with
response in HTML
format
Other networked
devices (datagram
communication)
J2ME
CLDC
Sandbox
HTTP/
Datagram