JAVA

Overview

Java programming language was originally developed by Sun Microsystems which was initiated by James Gosling and released in 1995 as core component of Sun Microsystems’ Java platform (Java 1.0 [J2SE]).

Java is one of the world’s most important and widely used computer languages, and it has held this distinction for many years. Unlike some other computer languages whose influence has weared with passage of time, while Java’s has grown.

The Java programming language is a high-level language that can be characterized by all of the following buzzwords:

  • Object Oriented − In Java, everything is an Object. Java can be easily extended since it is based on the Object model.
  • 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 the Virtual Machine (JVM) on whichever platform it is being run on.
  • Simple − Java is designed to be easy to learn. If you understand the basic concept of OOP Java, it would be easy to master.
  • Secure − With Java’s secure feature it enables to develop virus-free, tamper-free systems. Authentication techniques are based on public-key encryption.
  • Architecture-neutral − Java compiler generates an architecture-neutral object file format, which makes the compiled code executable on many processors, with the presence of Java runtime system.
  • Portable − Being architecture-neutral and having no implementation dependent aspects of the specification makes Java portable. Compiler in Java is written in ANSI C with a clean portability boundary, which is a POSIX subset.
  • Robust − Java makes an effort to eliminate error prone situations by emphasizing mainly on compile time error checking and runtime checking.
  • Multithreaded − With Java’s multithreaded feature it is possible to write programs that can perform many tasks simultaneously. This design feature allows the developers to construct interactive applications that can run smoothly.
  • Interpreted − Java byte code is translated on the fly to native machine instructions and is not stored anywhere. The development process is more rapid and analytical since the linking is an incremental and light-weight process.
  • High Performance − With the use of Just-In-Time compilers, Java enables high performance.
  • Distributed − Java is designed for the distributed environment of the internet.
  • Dynamic − Java is considered to be more dynamic than C or C++ since it is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time.

What Can Java Technology Do?

The general-purpose, high-level Java programming language is a powerful software platform. Every full implementation of the Java platform gives you the following features:

  • Development Tools: The development tools provide everything you’ll need for compiling, running, monitoring, debugging, and documenting your applications. As a new developer, the main tools you’ll be using are the javac compiler, the java launcher, and the javadoc documentation tool.
  • Application Programming Interface (API): The API provides the core functionality of the Java programming language. It offers a wide array of useful classes ready for use in your own applications. It spans everything from basic objects, to networking and security, to XML generation and database access, and more. The core API is very large; to get an overview of what it contains, consult the Java Platform Standard Edition 8 Documentation.
  • Deployment Technologies: The JDK software provides standard mechanisms such as the Java Web Start software and Java Plug-In software for deploying your applications to end users.
  • User Interface Toolkits: The JavaFX, Swing, and Java 2D toolkits make it possible to create sophisticated Graphical User Interfaces (GUIs).
  • Integration Libraries: Integration libraries such as the Java IDL API, JDBC API, Java Naming and Directory Interface (JNDI) API, Java RMI, and Java Remote Method Invocation over Internet Inter-ORB Protocol Technology (Java RMI-IIOP Technology) enable database access and manipulation of remote objects.

How Java Works?

Java is the first substantial language which is neither truly interpreted nor compiled; instead, a combination of the two forms is used. This method has advantages which were not present in earlier languages.

Platform-Independence

To understand the primary advantage of Java, you’ll have to learn about platforms. In most programming languages, a compiler (or interpreter) generates code that can execute on a specific target machine. For example, if you compile a C++ program on a Windows machine, the executable file can be copied to any other machine but it  will only run on other Windows machines but never another machine (e.g., a Mac or a Linux machine). A platform is determined by the target machine (along with its operating system). For earlier languages, language designers needed to create a specialized version of the compiler (or interpreter) for every platform. If you wrote a program that you wanted to make available on multiple platforms, you, as the programmer, would have to do quite a bit of additional work.  You would have to create multiple versions of your source code  for each platform.

Java succeeded in eliminating the platform issue for high-level programmers (such as you) because it has reorganized the compile-link-execute sequence at an underlying level of the compiler. Details are complicated but, essentially, the designers of the Java language isolated those programming issues which are dependent on the platform and developed low-level means to abstractly refer to these issues. Consequently, the Java compiler doesn’t create an object file, but instead it creates a bytecode file which is, essentially, an object file for a virtual machine.  In fact, the Java compiler is often called the JVM compiler (for Java Virtual Machine).

Consequently, you can write a Java program (on any platform) and use the JVM compiler (called javac) to generate a bytecode file (bytecode files use the extension .class). This bytecode file can be used on any platform (that has installed Java). However, bytecode is not an executable file.  To execute a bytecode file, you actually need to invoke a Java interpreter (called java). Every platform has its own Java interpreter which will automatically address the  platform-specific issues that can no longer be put off. When platform-specific operations are required by the bytecode, the Java interpreter links in appropriate code specific to the platform.

Other Advantages of Java

Most of the other features of Java had previously existed in various other programming languages (but never all at once).  Most explanations of these advantages (e.g., distributed programming, multi-threading, security) are well beyond the scope of this course. However, there are two features that I will briefly address.

Another feature that was introduced with the Java language is the ability to write special Java programs (called applets) that are designed to run on the World Wide Web. You could write a Java applet and put the bytecode on a web page; if anyone with a Java-enabled web browser goes to your web page, that applet bytecode will be downloaded to the browsing computer and executed within the web browser. Of course, this would not be possible without platform independence. This feature had a major effect on the rapid proliferation of Java and many instructors (including myself) taught programming using applet-based programs. However, for a variety of reasons, I have decided to postpone a discussion of applets (and more generally, graphic user interfaces) to the end of the course.

Java is also one of the first languages to be “library-based” in that the designers of the language have included a large number of pre-existing programs. A programmer can connect their program to these general purpose programs as needed. It frees up the programmer’s time since s/he doesn’t have to write as much code.

Application of Java

Java is widely used in every corner of world and of human life. Java is not only used in software but is also widely used in designing hardware controlling software components. There are more than 930 million JRE downloads each year and 3 billion mobile phones run java.

Following are some other usage of Java:

  • Developing Desktop Applications
  • Web Applications like Linkedin.com, Snapdeal.com etc
  • Mobile Operating System like Android
  • Embedded Systems
  • Robotics and games etc.
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