Download Java Overview (for Silberschatz chapter 3, setion 3

Java Overview (for Silberschatz chapter 3, section 3.7)
2/11/02 – NMG+
Note: all diagrams taken from PPT slide file for “Applied Operating Systems Concept”, 1st ed.,by
Silberschatz et. al., Wiley Publisher.

Java language characteristics:
“pure” object oriented
architecture-neutral
distributed
Multithreaded
Language syntax is “C-like” – Evolved out of C just as C++

Compiled output files (*.class) contain “bytecode” which will run on any implementation
of the “Java Virtual Machine” (JVM) – platform independent.
JVM is an interpreter that interprets the bytecode – analogous to interpretive BASIC.

Java: originally focused on Internet programming due to support of “applets” – programs
that run within (or under) a web browser.
Can also write and compile “stand-alone” programs which will run from the command line in
the context of JVM

Java: is a multithreaded language: multiple “threads” of control or flows within a given
Java “program module” ... threads actually reside in the JVM.

Java API: A large set pr “library” of useful utilities and other programs which can be
incorporated and used in any user program – analogous to the standard /runtime libraries for C
language. Two API’s: base (graphics, I/O, etc) and standard extension API (security, media and
others).
 Java Virtual Machine:
Class loader loads compiled programs of type .class
Interpreter executes bytecode words - one at a time, or it maybe a ==>
“Just-In-Time” compiler that turns bytecode words into native machine language (an incremental
compiler).
 Java platform consists of JVM and Java API.
The java platform provides machine independence and portability of compiled classes.
Java is portable, since Java programs are isolated from the hardware & software using
“byte” code in “Java Virtual Machine (JVM).
 Java Development environment: