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Fundamentals oF                                         3


                                             Java Programming








            In this  unit, you’ll learn how  to create  and run Java programs. However,  before  you start,  you need
            to understand what a program is. A computer program is a set of instructions given to a computer to
            perform a particular task. The instructions show what and how the computer should do it. Programming
            is  the  preparation  and  creation  of  computer  programs.  Programmers  write  programs  using  high-level

            programming languages  such as Java, C ++, Python, Ruby, and Scala. Computers, on the other hand, only
            know their own language, the so-called “machine language”. As a result, a compiler is needed to translate
            high-level  program  code  into  computer-understandable  machine  language  code.  After  the  program  is
            created, the machine code can be run on the computer where it was compiled such as Windows. If the
            program is to be run on a different platform, such as Mac, it must first be compiled for that platform before
            being run.

              3.1 IntroductIon to Java

            Java is a widely used high-level programming language used to develop a variety of computer programs such
            as database applications, desktop applications, web-based apps, mobile applications, and games. Instead of
            converting Java code to machine language code, the Java compiler translates it into Java bytecode (a highly
            optimized set of instructions). When bytecode (also known as a Java class file) runs on your computer, it is
            converted to machine code by a Java interpreter called the Java Virtual Machine (JVM). The advantage of this
            approach is that once the Java program is converted to bytecode, it can run on any platform (Windows, Linux,
            Mac, etc.). With the help of the JVM, Java programs are considered platform-independent and portable.
            Writing a Java program (compiling code into bytecode) requires a text editor (to write the code) and a Java
            compiler. There are many Java integrated development environments (IDEs) on the market, including text
            editors and Java compilers, making it much easier to create, compile, and run Java applications. Most of
            these can be downloaded for free from the internet. To build a Java app, use the open-source and free Java
            NetBeans IDE.
            3.1.1 Writing a Simple Java Program

            Let us write a simple Java program that displays Hello World! messages on the screen. Since this is the first
            Java program, you need to set up a programming environment. To do so , follow the steps given below:

             1   To start Net Beans, Double-click the Net Beans icon on your desktop. The Net Beans IDE will open.











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