Almost the Same Old Stuff - Beginning J2ME: From Novice to Professional - page 37

CHAPTER 4
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Almost the Same Old Stuff
A s we discussed in Chapter 1, one of the reasons you might be interested in MIDP as a plat-
form is that it's based on the Java programming language and the Java APIs. You'll also recall
that MIDP is built on top of the Connected, Limited Device Configuration (CLDC). The CLDC
contains most of the APIs that will look familiar to experienced Java programmers. As of this
writing, CLDC 1.0 is the most widely available version, but many newer devices are beginning
to support the CLDC 1.1 specification. We'll mention the differences between CLDC 1.0 and
CLDC 1.1 throughout this chapter.
In this chapter, we'll explore the java.lang , java.io , and java.util packages as defined in
the CLDC. We'll assume you're already familiar with the basic APIs of J2SE; we'll walk through
what's the same and what's different.
At the time of this writing (first quarter 2005), CLDC 1.1 and MIDP 2.0 have been imple-
mented on real devices from several manufacturers (Nokia, Siemens, Sony Ericsson, just to
name a few). The industry-wide endorsement of the JTWI (JSR 185) has prompted the rapid
adoption of MIDP 2.0. Although some JTWI devices only implement MIDP 2.0 over CLDC 1.0,
it is anticipated most new devices will be implemented on top of CLDC 1.1.
No Floating Point in CLDC 1.0
CLDC 1.0 does not support floating-point types at all. That means there are no float or double
primitive types. The corresponding wrapper types, java.lang.Float and java.lang.Double ,
have also been eliminated.
Floating-point support is absent in CLDC 1.0. On CLDC 1.0 devices, if calculations involving
fractional numbers are important to your application, you can perform them in software. One
implementation (using fixed-point integers) can be found at http://home.rochester.rr.com/
ohommes/MathFP/ .
CLDC 1.1 includes floating-point support, the primitive types double and float , and the
wrapper types Double and Float . Various other classes have been modified for floating-point
support in CLDC 1.1, but the changes are minor.
java.lang
Table 4-1 and Table 4-2 list the classes and interfaces of java.lang and java.lang.ref in both
J2SE (SDK version 1.4.2) and CLDC. The CLDC columns indicate whether the class is identical
to its J2SE counterpart, is present with API differences, or is not present at all.
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