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.
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
is hidden and cannot be accessed by external functions
-Objects can communicate with each other through functions
-New data and functions can be easily addedJava has powerful features. The following are some of them:-
Portable (Platform Independent)
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.
Four principles of Object Oriented Programming are
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 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.
* Hides the implementation details of a class.
* Forces the user to use an interface to access data
* Makes the code more maintainable.
Inheritance is the process by which one object acquires the properties of another object.
Polymorphism is the existence of the classes or methods in different forms or single name denoting different