Java...how does it all start?


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Thread: Java...how does it all start?

  1. #1
    Mike Skvarenina Guest

    Java...how does it all start?


    OK, so I am an experienced computer programmer in VB and RPG getting ready
    to make the leap to Java! But to this day I don't see the big picture.
    Do I make .exe's with Java or do all my programs run out of a browser. If
    I always run out of a browser, I guess the database resides on the same machine
    as the web server?

    I guess I am looking for a graphical overview of how Jva intergrates with
    the computer world...or at least a good explaination. Can anyone shed some
    light here?


  2. #2
    Kent Guest

    Re: Java...how does it all start?


    Hi,

    I think I can explain most of what you're asking. Java is, in theory, platform
    independent. That is, a compiled Java class can be executed on any Java-supporting
    system.

    When a .java file is compiled, it is compiled into Java Byte Codes (stored
    in .class files). These class files are executed using the Java Virtual Machine
    (JVM). The JVM is the platform-dependent software.

    To execute a Java class you will need a JVM on your machine. The JVM converts
    the byte codes into machine code specific to your machine. So, in effect,
    there is an extra layer between the 'executable'.

    Java can be used on the server (eg. a Java class to interact with a database
    that also resides on the server) or on the client (an Applet for example).
    Java is not limited to web purposes. For example, I could write a Java program
    to encrypt/decrypt a PIN for a project I'm working on. I can compile and
    run this Java program via the command line using 'javac' (java compiler)
    and 'java' respectively.

    For a database to be useful from a web point of view, it really needs to
    reside on the server. You can't expect each user to download the database,
    plonk it on their machine, do their thing, then upload the database again!

    Having the database on the server allows all users to use the same data at
    effectively the same time. Using JSP (Java Server Pages) you can invoke methods
    on Java classes (sitting on the server) to do database interactions (save
    records, return records etc.).

    I hope this explains a bit...

    Kent


    "Mike Skvarenina" <mskvarenina@usa.net> wrote:
    >
    >OK, so I am an experienced computer programmer in VB and RPG getting ready
    >to make the leap to Java! But to this day I don't see the big picture.


    >Do I make .exe's with Java or do all my programs run out of a browser.

    If
    >I always run out of a browser, I guess the database resides on the same

    machine
    >as the web server?
    >
    >I guess I am looking for a graphical overview of how Jva intergrates with
    >the computer world...or at least a good explaination. Can anyone shed some
    >light here?
    >



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