1.
JAVA EVOLUTION
BY
HARSHA BATRA
ASSISTANT PROFESSOR
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2.
Introduction
Java is a another programming language but with a
difference that it is purely object-oriented. It is most
complete programming language available today. It is also
secure, making it well-suited for Internet programming.
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3.
Contents
1. Java - Introduction
2. History of Java
3. Features of Java
4. Java Environment
5. JRE Components

4.
Java - Introduction
Java is a set of computer software and specifications developed by Sun Microsystems, later
acquired by Oracle Corporation, that provides a system for developing application software and
deploying it in a cross-platform computing environment.
Java is used in a wide variety of computing platforms from embedded devices and mobile
phones to enterprise servers and supercomputers.
Java is fast, secure, and reliable. From laptops to datacenters, game consoles to scientific
supercomputers, cell phones to the Internet, Java is everywhere!
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5.
History of Java
1) James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in
June 1991. The small team of sun engineers called Green Team.
2) Originally designed for small, embedded systems in electronic appliances like set-top boxes.
3) Firstly, it was called "Greentalk" by James Gosling and file extension was .gt.
4) After that, it was called Oak and was developed as a part of the Green project.
5) In 1995, Oak was renamed as "Java" because it was already a trademark by Oak Technologies.
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6.
Features of Java
Compiled and Interpreted: Java has both Compiler and Interpreter Feature. Program is First Compiled
and then Interpreted .In the first step after Compilation it creates Bytes Codes rather than Machine code.
Then in second step Bytes Code is Converted into the Machine Language with the help of the Interpreter.
Platform Independent:- Java is Platform Independent means program of java is Easily transferable. As
mentioned above that after Compilation bytes code gets created this can be transferred easily to
another Computer. It is not necessary for computers having same Operating System in which the code of
the java was created and executed.
Object-Oriented:- We Know that Java is purely OOP Language i.e. all the Code is Written into the classes
and Objects. For this feature java is most popular language.
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7.
Simple Small and Familiar:- is a simple Language Because it contains many features of other Languages like
c and C++ and Java Removes Complexity because it doesn’t use pointers, Storage Classes and Go to
Statements and java Doesn’t support Multiple Inheritance
Multithreaded and Interactive:- Java uses Multithreaded Techniques For Execution. Program of java is
divided into the Small parts those are Executed by Compiler of java itself. Java is Called as Interactive
because Code of java Supports CUI as well as GUI Programs.
Secure: Java was designed with security in mind. As Java is intended to be used in networked/distributed
environments so it implements several security mechanisms to protect against malicious code that might try
to invade file system. For example: The absence of pointers in Java makes it impossible for applications to
gain access to memory locations without proper authorization as memory allocation and referencing model
is completely opaque to the programmer and controlled entirely by the underlying run-time platform .
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8.
Distributed:- The program in java can be design to run on computer networks. Java provides an extensive library of
classes for communicating, using TCP/IP protocols such as HTTP and FTP. This makes creating network connections
much easier than in C/C++. You can read and write objects on the remote sites via URL with the same ease that
programmers are used to when read and write data from and to a file. This helps the programmers at remote
locations to work together on the same project.
High performance: Java programs are complied to portable intermediate form know as bytecodes, rather than to
native machine level instructions and JVM executes Java bytecode on. Any machine on which it is installed. This
architecture means that Java programs are faster than program or scripts written in purely interpreted languages
but slower than C and C++ programs that compiled to native machine languages.
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9.
Architectural Neutral: One of the key feature of Java that makes it different from other programming
languages is architectural neutral (or platform independent). This means that the programs written on one
platform can run on any other platform without having to rewrite or recompile them. In other words, it
follows 'Write-once-run-anywhere' approach.
Java programs are compiled into byte-code format which does not depend on any machine architecture
but can be easily translated into a specific machine by a Java Virtual Machine (JVM) for that machine. This
is a significant advantage when developing applets or applications that are downloaded from the Internet
and are needed to run on different systems.
Dynamic and Extensible Code:- java is Object-Oriented and hence follows Inheritance which supports
code-reusability and the built in Functions of java and Classes can also be reused.
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10.
Java Environment
Java environment includes a large number of development tools and hundreds of classes and methods. The
development tools are a part of JDK (Java Development Kit), and classes and methods are a part of JSL (Java
Standard Library), also known as API(Application Programming Interface).
Java Development Kit
JDK comes with a collection of tools used for developing and running Java programs. They include:
1. Appletviewer (for viewing Java applets) 5. javah (for C header files)
2. javac (java compiler) 6. javadoc (for HTML documents)
3. java (java interpreter) 7.jdb (java debugger)
4. javap (java disassembler)
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11.
JRE Components
The JRE is the software environment in which programs are compiled for a typical JVM (Java Virtual Machine)
implementation can run. The runtime system includes:
1. JVM: It is a program that interprets the intermediate Java byte code and generates the desired output. It is because
of JVM and byte code that make Java programs portable.
2. Runtime class libraries: These are a set of core class libraries that are required for the execution of Java programs.
3. User Interface toolkits: AWT (Abstract Windows Toolkit) and Swing are examples of toolkits that support varied input
methods to interact with application program.
4. Deployment Technologies: JRE comprises of Java Plug-in and Java Web Start.
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12.
1. JVM
The JVM is an abstract computing machine, having an instruction set that uses memory. Virtual machines are
often used to implement a programming language. The JVM is the cornerstone of the Java programming language.
It is responsible for Java's cross-platform portability and the small size of its compiled code.
The Solaris JVM is used to execute Java applications. The Java compiler, javac, outputs bytecodes and puts them
into a .class file. The JVM then interprets these bytecodes, which can then be executed by any JVM
implementation, thus providing Java's cross-platform portability. The next two figures illustrate the traditional
compile-time environment and the new portable Java compile-time environment.
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13.
1.1 Multithreading JVM
The Java programming language requires that multithreading (MT) programs be supported. All Java interpreters
provide an MT programming environment. However, many of these interpreters support only uniprocessor
multithreading, so Java program threads are executed one at a time.
The Solaris JVM interpreter takes full advantage of multiprocessor systems by using the intrinsic Solaris
multithread facilities. These allow multiple threads of a single process to be scheduled simultaneously onto
multiple CPUs. An MT Java program run under the Solaris JVM will have a substantial increase in concurrency over
the same program run on other platforms.
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14.
1.2 Sun Just-In-Time (JIT) Compiler
The Sun Java JIT compiler, an integral part of the Solaris JVM, can accelerate execution performance many times
over previous levels. Long-running, compute-intensive programs show the best performance improvement.
JIT Compile Process
When the JIT compiler environment variable is on (the default), the JVM reads the .class file for interpretation
and passes it to the JIT compiler. The JIT compiler then compiles the bytecodes into native code for the platform
on which it is running. The next figure illustrates the JIT compile process.
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15.
4. Deployment Technologies
JRE comprises of the following key deployment technologies:
1. Java Plug-in: Enables the execution of Java applet on the browser.
2. Java Web Start: Enables remote deployment of the application. With Web Start, users can launch an
application from the Web browser without going through installation procedure.