MARWARI COLLEGE, RANCHI
(AN AUTONOMOUS UNIT OF RANCHI UNIVERSITY FROM 2009)
- Prakash Kumar, Dept. of CA
-Raju Manjhi, Dept. of CA
__________________________________________________________________________________
JAVA
BCA- Sem-II(CBCS)
Java history: It starts from Green Team. Java team members (also known as Green
Team), initiated a revolutionary task to develop a language for digital
devices such as set-top boxes, televisions etc.
Java is used in internet programming, mobile devices, games,
e-business solutions etc. There are given the major point that describes the
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.
Some Java versions
and its year of release:-
1.
JDK Alpha and Beta (1995)
2.
JDK 1.0 (23rd
Jan, 1996)
3.
JDK 1.1 (19th
Feb, 1997)
4.
J2SE 1.2 (8th
Dec, 1998)
5.
J2SE 1.3 (8th
May, 2000)
6.
J2SE 1.4 (6th
Feb, 2002)
7.
J2SE 5.0 (30th
Sep, 2004)
8.
Java SE 6 (11th
Dec, 2006)
9.
Java SE 7 (28th
July, 2011)
10.
Java SE 8 (18th
March, 2014)
11.
Java SE 9 (21st
September 2017)
12.
Java SE 10 (20th
March 2018)
13.
Java SE 11 (25th
September 2018)
14.
Java SE 12 (19th
March 2019)
15.
Java SE 13 (17th
September 2019)
16.
Java SE 14 (17th
March 2020)
17.
Java SE 15 (Expected
in September 2020)
Java is Simple
According to Sun, Java language is simple because:
|
Syntax is based on C++ (so easier for programmers to learn it
after C++).
|
Removed many confusing and/or rarely-used features e.g.,
explicit pointers, operator overloading etc.
|
No need to remove unreferenced objects because there is
Automatic Garbage Collection in java.
|
Object-oriented
Object-oriented means we organize our software as a combination
of different types of objects that incorporates both data and behaviour.
|
Object-oriented programming (OOPs) is a methodology that
simplifies software development and maintenance by providing some rules.
|
Basic concepts of OOPs are:
|
1. Object
2. Class
3. Inheritance
4. Polymorphism
5. Abstraction
6. Encapsulation
|
Features of Java:
1.
Platform Independent
A platform is the hardware or software environment in which a
program runs. There are two types of platforms software-based and
hardware-based. Java provides software-based platform. The Java platform
differs from most other platforms in the sense that it's a software-based
platform that runs on top of other hardware-based platforms. It has two
components:
1. Runtime Environment
2. API(Application
Programming Interface)
|
Java code can be run on multiple platforms e.g.Windows, Linux,
Sun Solaris, and Mac/OS etc. Java code is compiled by the compiler and
converted into bytecode.This bytecode is a platform independent code because
it can be run on multiple platforms i.e. Write Once and Run Anywhere(WORA).
|
2.
Secured
Java is secured because:
|
·
No explicit pointer
·
Programs run inside virtual machine sandbox.
|
·
Classloader- adds security by
separating the package for the classes of the local file system from those
that are imported from network sources.
·
Bytecode Verifier- checks the code
fragments for illegal code that can violate access right to objects.
·
Security Manager- determines what
resources a class can access such as reading and writing to the local disk.
|
These securities are provided by java language. Some security
can also be provided by application developer through SSL,JAAS,cryptography
etc.
|
3.
Robust
Robust simply means strong. Java uses strong memory management.
There are lack of pointers that avoids security problem. There is automatic
garbage collection in java. There is exception handling and type checking
mechanism in java. All these points makes java robust.
|
4.
Architecture-neutral
There are no implementation dependent features e.g. size of
primitive types is set.
Central issue for the Java designers was that of code longevity
and portability. One of the main problems facing programmers is that no
guarantee exists that if you write a program today, it will run tomorrow—even
on the same machine. Operating system upgrades, processor upgrades, and
changes in core system resources can all combine to make a program
malfunction. The Java designers made several hard decisions in the Java
language and the Java Virtual Machine in an attempt to alter this situation.
Their goal was “write once; run anywhere, anytime, forever.” To a great
extent, this goal was accomplished.
|
5.
Portable
We may carry the java bytecode
to any platform.
|
6.
High-performance
Java is faster than traditional interpretation since byte code
is "close" to native code still somewhat slower than a compiled
language (e.g., C++)
|
7.
Distributed
We can create distributed applications in java. RMI and EJB are
used for creating distributed applications. We may access files by calling
the methods from any machine on the internet.
|
8.
Multi-threaded
A thread is like a separate program, executing concurrently. We
can write Java programs that deal with many tasks at once by defining multiple
threads. The main advantage of multi-threading is that it shares the same
memory. Threads are important for multi-media, Web applications etc.
Creating First Program
Let's create the hello baba program:
class A
{
public static void main(String args[])
{
System.out.println("Hello Baba! It’s Java");
}
}
Save this
file as A.java
Compile:
|
javac A.java
|
Execute:
|
java A
|
Understanding first java program
Let's see what is the meaning of class, public, static, void,
main, String[], System.out.println().
· class keyword is used to
declare a class in java.
· public keyword is an access
modifier which represents visibility, it means it is visible to all.
· static is a keyword, if we
declare any method as static, it is known as static method. The core advantage
of static method is that there is no need to create object to invoke the static
method. The main method is executed by the JVM, so it doesn't require to create
object to invoke the main method. So it saves memory.
· void is the return type of
the method, it means it doesn't return any value.
· main represents startup of
the program.
· String[] args is used for command line
argument.
· System.out.println() is used print statement.
Note:
Valid java main method signature
1.
public static void main(String[] args)
2.
final strictfp public static void main(String[] args)
Tq sir ����for the useful notes ��
ReplyDelete