Java Reference
In-Depth Information
Java Micro Edition
The
Java Micro Edition (Java ME)
—a subset of Java SE—is geared toward developing
applications for resource-constrained embedded devices, such as smartwatches, MP3 play-
ers, television set-top boxes, smart meters (for monitoring electric energy usage) and more.
Computers can perform calculations and make logical decisions phenomenally faster than
human beings can. Many of today's personal computers can perform billions of calcula-
tions in one second—more than a human can perform in a lifetime.
Supercomputers
are
already performing
thousands of trillions (quadrillions)
of instructions per second! China's
National University of Defense Technology's Tianhe-2 supercomputer can perform over
33 quadrillion calculations per second (33.86
petaflops
)!
5
To put that in perspective,
the
Tianhe-2 supercomputer can perform in one second about 3 million calculations for every per-
son on the planet!
And—these supercomputing “upper limits” are growing quickly.
Computers process data
under the control of sequences of instructions called
com-
puter programs
.
These software programs guide the computer through ordered actions
specified by people called computer
programmers
.
In this topic, you'll learn a key pro-
gramming methodology that's enhancing programmer productivity, thereby reducing
software development costs—
object-oriented programming
.
A computer consists of various devices referred to as hardware (e.g., the keyboard,
screen, mouse, hard disks, memory, DVD drives and processing units)
.
Computing costs
are
dropping dramatically
, owing to rapid developments in hardware and software technol-
ogies. Computers that might have filled large rooms and cost millions of dollars decades
ago are now inscribed on silicon chips smaller than a fingernail, costing perhaps a few dol-
lars each. Ironically, silicon is one of the most abundant materials on Earth—it's an ingre-
dient in common sand. Silicon-chip technology has made computing so economical that
computers have become a commodity.
Every year, you probably expect to pay at least a little more for most products and services.
The opposite has been the case in the computer and communications fields, especially
with regard to the hardware supporting these technologies. For many decades, hardware
costs have fallen rapidly.
Every year or two, the capacities of computers have approximately
doubled
inexpen-
sively. This remarkable trend often is called
Moore's Law
, named for the person who iden-
tified it in the 1960s, Gordon Moore, co-founder of Intel—the leading manufacturer of
the processors in today's computers and embedded systems. Moore's Law and related
observations apply especially to the amount of memory that computers have for programs,
the amount of secondary storage (such as disk storage) they have to hold programs and
data over longer periods of time, and their processor speeds—the speeds at which they
exe-
cute
their programs (i.e., do their work).
