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Java - 'Hello World' for absolute beginners

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Submitted on: 1/2/2015 5:41:00 PM
By: michael worthington (from psc cd)  
Level: Beginner
User Rating: By 2 Users
Compatibility: Java (JDK 1.2)
Views: 2015
 
     the purpose of this tutorial is to teach beginner java programmers how to make their first program. it is a simple 'Hello World' program that they make, but it covers a lot of basics to writing, compiling, and running a program on your computer.

 
				



INTRO TO JAVA - WRITTEN BY: M.WORTHINGTON [12.01.01]

...so you've decided to learn a little java. yes this is java, not java srcipt. i'll be making tutorials as often as possible to share my knowledge of the programming language and allow you to learn something new.
...first let me share my background on the topic. i'm currently a college freshman and am studying the language for the first time. i've had experience in visual basic, basic, and c++. so while i'm not an expert in java, i can still share what i learn each week in class. so basically you'll be getting a free college education of java.
...if you've ever read and programming book they spend a couple chapters explaining computers and how programs methodically work. i'm not going to do that. for you to learn from my tutorials you'll have to have some basic understanding of the world of programming. even if you don't, you should still be able to learn from me.
...so here we go

while java is an internet language, you program it and run it right on your computer. first, you're going to need the java runtimes on your computer. i suggest going to http://java.sun.com to download JavaTM 2 SDK, Standard Edition, v 1.2.2. follow all of the installation instructions, because you will need to edit one line of text in your autoexec batch file. the instructions from the program should explain what to do. if you are having trouble, hit up the message boards for help.

to create your programs, you can use notepad or wordpad (or basically any text editor). i use notepad. java is a case sensitive language, so you will have to go through the trouble of hitting shift or caps lock for making sure all the code is formatted properly.

OBJECTIVE
in tradition of things, your first java program will be a 'Hello World' one. basically, the idea behind this will be to learn how to create a program you can compile and run.

PROGRAM

public class FirstProgram
{
public static void main(String[] args)
{
System.out.println("Hello World");
} //main
} //class

ABOUT THE PROGRAM
we are creating a java class in this program. as well, we are putting a main function within it. in this program, the name of our class is 'FirstProgram'. the brackets { and } begin and end the class as well as the main method. in the main method is the line 'System.out.println("Hello World");' this code is telling the computer to print out on one line 'Hello World' (minus the single quotes). what you want to be printed is what you want to put between the quotes. the semi-colon ';' ends the line of code and goes to the next of code. since the next line of code is simply are bracket closing the main method. it goes to the next. and then the class is closed. the double slashes '//' are for commenting out text. they become vital in complex programs when you want to make notes by your code. everything to the right of the slashes on the same line does not get compiled and is not code, so write whatever you want.


COMPILING & RUNNING
when you save your file, you must type on the .java extension as well as put the file in quotes, as seen here. the name of the file must be the name of the class. in this case, it must be 'FirstProgram' and the .java extension. remember, java is case sensitive.

to compile and test out your programs, you need to use MS-DOS. in case you have no idea about DOS commands, there are a few you need to know. use this picture to assist yourself. to open MS-DOS, go to START>RUN and type 'command'. while in DOS you need to basically, when trying to move from folder to folder 'cd' is the command you need. example: 'cd..' will move you from C:\Windows to C:\ and 'cd jdk1.2.2' will move you from C:\ to C:\jdk1.2.2\. when you are in MS-DOS and at the C:\jdk1.2.2\bin (which is the default of where you should be saving your java files and compiling them) type 'javac'. do this one time only, just to install it.

now to compile your program FirstProgram.java, type 'javac FirstProgram.java' and hit enter. if it compiles properly with no errors, you should get a new line simply showing the directory you are in. now to run the program you need to type 'java FirstProgram' and hit enter. for this particular program, you should get the print out 'Hello World' on the next line. SUCCESS!

you've made your first java program. congratulations, computer nerd. now, try making your program print out other stuff. make it print out multiple lines by using the code you already know.

please let me know what you think of this tutorial by going to the message boards or the contact page and submitting your comments.


 


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