Welcome to Java—the world’s most widely used computer programming
language. You’re
already familiar with the powerful tasks computers perform. Using this
textbook, you’ll
write instructions commanding computers to perform those kinds of tasks.
Software (i.e.,
the instructions you write) controls hardware (i.e., computers).
You’ll learn object-oriented programming—today’s key programming
methodology.
You’ll create and work with many software objects in this text.
Java is the preferred language for meeting many organizations’
enterprise programming
needs. Java has also become the language of choice for implementing
Internet-based
applications and software for devices that communicate over a network.
In use today are more than a billion general-purpose computers and
billions more
Java-enabled cell phones, smartphones and handheld devices (such as
tablet computers).
According to a study by eMarketer, the number of mobile Internet users
will reach approximately
134 million by 2013.1 Other studies have projected smartphone sales to
surpass
personal computer sales in 20112 and tablet sales to account for over
20% of all personal
computer sales by 2015.3 By 2014, the smartphone applications market is
expected to
exceed $40 billion,4 which is creating significant opportunities for
programming mobile
applications.
Characteristics of Java
•Java is
simple
•Java is
object-oriented
•Java is
distributed
•Java is
interpreted
•Java is
robust
•Java is
secure
•Java is
architecture-neutral
•Java is
portable
•Java’s
performance
•Java is
multithreaded
•Java is dynamic
Java life cycle
•Java programs normally undergo four phases
–Edit
•Programmer writes program (and stores program on disk)
–Compile
•Compiler creates bytecodes from program (.class)
–Load
•Class loader stores bytecodes in memory
–Execute
•Interpreter: translates bytecodes into machine language
• Source code (.java) – A typed java program using an editor
• Compiled into Byte codes (.class) , as (.exe) in c++
– The Java Application Programming Interface
(API)
–a large collection of ready-made software components. It is grouped
into libraries of related classes and interfaces; these libraries are known as
packages.
– Java Virtual Machine (JVM) - a part of the JDK and the
foundation of the Java platform
– A virtual machine (VM) is a software application that simulates
a computer but hides the underlying operating system and hardware from the
programs that interact with it.
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