Introduction to Java Programming
Introduction to Computer Science using Java
Java is a simple and yet powerful object oriented programming language and it is in many respects similar to C++. Java
originated at Sun Microsystems, Inc. in 1991.
It was conceived by James Gosling, Patrick Naughton, Chris Warth, Ed Frank, and Mike Sheridan at Sun Microsystems, Inc. It was developed to provide a platform-independent programming language.
This site gives you an Introduction to Java Programming
accompanied with many java examples. Its a
complete course in java programming for beginners to
advanced java.
Platform independent
Unlike many other programming languages including C and C++ when Java is compiled, it is not compiled into platform specific machine, rather into platform independent byte code. This byte code is distributed over the web and interpreted by virtual Machine (JVM) on whichever platform it is being run.
Java Virtual Machine
What is the Java Virtual Machine? What is its role?
Java was designed with a concept of ‘write once and run everywhere’. Java Virtual Machine plays the central role in this concept. The JVM is the environment in which Java programs execute. It is a software that is implemented on top of real hardware and operating system. When
the source code (.java files) is compiled, it is translated
into byte codes and then placed into (.class) files. The JVM
executes these bytecodes. So Java byte codes can be thought of as the machine language of the JVM. A JVM can either interpret the bytecode one instruction at a time or the bytecode can be compiled further for the real microprocessor using what is called a
just-in-time compiler. The JVM must be implemented on a particular platform before compiled programs can run on that platform.
Object Oriented Programming
Since Java is an object oriented programming language it has following
features:
- Reusability of Code
- Emphasis on data rather than procedure
- Data is hidden and cannot be accessed by external functions
- Objects can communicate with each other through functions
- New data and functions can be easily added
Java has powerful features. The following are some of them:-
Simple
Reusable
Portable (Platform Independent)
Distributed
Robust
Secure
High Performance
Dynamic
Threaded
Interpreted
Object Oriented Programming is a method of
implementation in which programs are organized as
cooperative collection of
objects, each of which represents an instance of a
class, and whose classes are all members of a hierarchy
of classes
united via inheritance relationships.
OOP Concepts
Four principles of Object Oriented Programming are
Abstraction
Encapsulation
Inheritance
Polymorphism
Abstraction
Abstraction denotes the essential characteristics of an
object that distinguish it from all other kinds of
objects and
thus provide crisply defined conceptual boundaries,
relative to the perspective of the viewer.
Encapsulation
Encapsulation is the process of compartmentalizing the
elements of an abstraction that constitute its structure
and
behavior ; encapsulation serves to separate the
contractual interface of an abstraction and its
implementation.
Encapsulation
* Hides the implementation details of a class.
* Forces the user to use an interface to access data
* Makes the code more maintainable.
Inheritance
Inheritance is the process by which one object acquires
the properties of another object.
Polymorphism
Polymorphism is the existence of the classes or methods
in different forms or single name denoting different
implementations.
Java is Distributed
With extensive set of routines to handle TCP/IP protocols like HTTP and FTP java can open and access the objects across net via URLs.
Java is Multithreaded
One of the powerful aspects of the Java language is that it allows multiple threads of execution to run concurrently within the same program A single Java program can have many different threads executing independently and continuously. Multiple Java applets can run on the browser at the same time sharing the CPU time.
Java is Secure
Java was designed to allow secure execution of code across network. To make Java secure many of the features of C and C++ were eliminated. Java does not use Pointers. Java programs cannot access arbitrary addresses in memory.
Garbage collection
Automatic garbage collection is another great feature of Java with which it prevents inadvertent corruption of memory. Similar to C++, Java has a new operator to allocate memory on the heap for a new object. But it does not use delete operator to free the memory as it is done in C++ to free the memory if the object is no longer needed. It is done automatically with garbage collector.
Java Applications
Java has evolved from a simple language providing interactive dynamic content for web pages to a predominant enterprise-enabled programming language suitable for developing significant and critical applications. Today,
It is used for many types of applications including Web based applications, Financial applications, Gaming applications, embedded systems, Distributed enterprise applications, mobile applications, Image processors, desktop applications and many more.
This site outlines the building blocks of java by stating
few java examples along with some java tutorials.
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