Learning Java Without Tears

NOTE: Please i do not expect everybody to read this on-line, you can copy the pages to a storage device
    and take time to go through it or you can also print it out.

    Welcome to this thread. Having seen some threads in this forum, I'm happy that so many people
in Nigeria are interested in learning Java. So I have decided to run a couple of threads as
my contribution to developing a strong Java Community in Nigeria. So, if u are among the lucky
ones that have decided to get started with learning Java, never mind, i am here to just get
you started.
   Learning Java could be fun and frustrating, depending on the angle you look at it
from.But I'm promising you that I am going to take it real slow and down to earth. I am also going to
go about it from the professional way i.e after finishing, if we ever finish, you should be
strong enough to add little effort and start hitting certification level. So let's get the ball
rolling with the requirements.

1.   To learn Java, of course you need a Java Development Tool (jdk) now called J2SE (Java 2 Standard Edition)
from 5.0 version (Code named Tiger). There is a lot of improvement in the new edition, in fact there is a
new version (Code named Mustang) already out but still at a beta (development) stage, the final version
should be out soonest. But be rest assured that it is backward compatible. But Version 5.0 is recommended.
It can be downloaded, which ever version you need from this link.

     http://java.sun.com/j2se/1.5.0/download.jsp

It is recommended to use Sun Download Manager (SDM) to download the J2SE else you are going to have a frustrating
time downloading it. The SDM can be downloaded from this link and it's easy to use. Read the read me file after
installing it to get cracking.

     http://www.sun.com/download/

2. Next, you are going to need a java aware text editor, i will recommend TextPad, there is a free evaluation
version you can use. I do not recommend using Integrated Development Environment (IDE) for now. They do shield you
from the real details of the language, and more so, they will always add some IDE specific codes to your application,
this might confuse you. Also debugging your application could be difficult, if you don't know how errors are handled
in java. TextPad can be downloaded from this link.

    http://www.textpad.com/download/

3.    Now that we have all the needed software requirements, installing the J2SE easy for windows but for Linux
you have to do some tweeking to get it and running.For Linux users, if you are unable to install it, please
feel free to post your problems, promise to sort it with you. Next thing is to configure our system and
development environment. You need to add java to your system classpath. If you don't know what is classpath,
never mind, i will explain. It's just a way of telling the system where to look for executable commands. Like
if u type "dir" in your DOS prompt, the system list the content of a directory, because DOS commands are added
to the classpath by default. So let's set the classpath.


      a. Right click My Computer icon on the desktop.
      b. Select properties.
      c. On the System Properties dialog box, select Advanced tab.
      d. Click on the Environment Variables button at the bottom.
      e. On the System Variables box, select Path under Variables, click Edit button.
      f. An Edit System Variable dialog box will show.
      g. In the Variable Value text Field, move your cursor to the beginning and add the path to
      your J2SE bin folder. eg

            C:\Program Files\Java\jdk1.5.0\bin,.

      click all the OK to take you back to Environmental Variables dialog box. Here, we are just going
      to add another simple System Variable, it for tools that depend on java to run. so
      Click the New button, A new System Variable dialog box appears. Just fill as stated below.

      Variable Name: JAVA_HOME
      Variable Value: C:\Program Files\Java\jdk1.5.0      - don't add the bin folder

      after this you can click all the OKs. Be warned, not to remove anything from the path when editing, if u do,
      your system might become unstable. So be careful. So, we are through with that. O boy no give up ooh.

      To test if everything went kool, click start, run, type cmd and hit enter. Na just to open Dos prompt o.
      Type javac
      hit enter, you should get a message like this.

      Microsoft Windows XP [Version 5.1.2600]
     (C) Copyright 1985-2001 Microsoft Corp.

     C:\Documents and Settings\Omo>javac
     Usage: javac <options> <source files>
     where possible options include:
       -g                         Generate all debugging info
       -g:none                    Generate no debugging info
       -g:{lines,vars,source}     Generate only some debugging info
       -nowarn                    Generate no warnings
       -verbose                   Output messages about what the compiler is doing
        <more lines here>


If you get this message all de kampe. If you don't get this message, no yawa, some systems might require a restart,
so do it, if yawa still gas, ma boy, sorry you have to go all over the process again. It's never been easy, getting
it right the first time.

4. Na wa o. I bet you, this  is going to be the longest part, we will ever get. It's nice we learn to get it right from
the beginning. Don't worry, this is the last paragraph for today. Setting our development environment. Java has
a recommended file standard structure you should follow, for now we will be doing it ourselves.But in real production
where you have hundreds of sources and class files, you will  be using tools like Ant to arrange your file structures. I will just
list the structure.

   a. Create a project directory that will contain all our projects folder.

         C:\project

   b. Create a sub directory, let's call it lecture1 (initial small letter), the name of our current project.

        C:\project\lecture1

   c. Create a sub folder for lecture1, name it src  -   it must be named src, source codes (what you write) goes into this folder.

        C:\project\lecture1\src

   d. Create another sub folder for lecture1, name it classes  - must also be named classes and your class files(compiled code) sit here.

        C:\project\lecture1\classes

So now we are ready to start the party, but before we go, let's look at area where most beginners encounter problems.Take note.

     1. Java is highly type checked. Mean the javac (compiler) will make sure you follow the rules. No short cuts.

           a and A are not the same. lagos and Lagos not same, so Lagos must be Lagos throughout your code.

     2.  White space are ignored. That is spaces between statements except for few exception like in classes,methods and
     variables declaration. (if you don't understand, don't panic, we go jump am pass).

     3. Class declaration must start with { and end with }.

     4. Method declaration must have () immediately after it's name and like classes must start and
     end with {}.

     5. Every statement must terminiate with ;

Though there are more, but these are what i feel are the most common,
So my boy, me i dey check out. Take your time to digest it and make effort to get the required tool, because
by next class we will write our first program and explain some concept in java using a simple program.
Wish you all the best. To all, including  the gurus and alike, please your criticism,observation,contribution and
recommendations are welcome.

Recommended free training site. Highly rated.

     www.javaranch.com

Recommended Text book

HeadFirst Java 5.0 (Second Edition) by Kathy Sierra and Bert Bates.
HeadFirst Java (First Edition - covers version 1.4) by Same authors

Recommended books for Certifications.

Sun Certified Java Programmer

Sun Certified Java Programmer 1.4 Exam Guide by Kathy Sierra and Bert Bates.
Note:
The 5.0 version seems not to as good as the 1.4 version

Sun Certified Java Associate

no books yet. It's a new exam for entry level.

Sun Certified Web Component Developer 1.4.

HeadFirst Servlet and JSP ( rated best in the category) - lots of hands on practice
  - simulation of real development paractice

Sun Certified Business Component Developer 1.3.

SCBCD EXAM STUDY KIT by Paul Sanghera (free pdf version available on-line)
EJB Specification 2.0 from Sun.
HeadFirst EJB by Kathy Sierra and Bert Bates (Very good teaching approach but some error, corrections available on-line).
Mastering Enterprise JavaBeans 3rd Edition by Ed Roman and co (free pdf version available on-line)

Recommended Bookshop in Lagos.

Ebuy (Prices are ok, extra 1k or 1.5k above on-line prices).
Delivering within 2 to 3 weeks.
Call Seun 01-4751491 or
Dolapo 08029494655

There is always a mode in which you can create a blank .java file, write what you want to write, and compile!  I agree that when you struggle with command line IDE may be easy but why struggle in the first place?

Momoh-mi, am in for this, please go on teaching, am learning

In the last tutorial, we looked at how to install and configure our Java environment on
both windos and Linux systems. We also looked at how to setup the java development environment
as required in real world production.
   So, today, we are going to use a simple program to illustrate the fundamentals of java.
When you write a java program, what happen after that.What role those the compiler play, what is
a Java Virtual Machine and what does it do and how does it read your applications.So, we kick off
with the program as shown below. Please note the file name and the class MUST the SAME. And
must be saved with a java file extension ie
MyFirstApp.java as shown at the bottom of this post. Ok, pause, look at at the example.
     
       
   Now think of development environment. We need to create a folder, the name should be the same with our project name.
This is not required but recommended. So our file structure should be like this.

          C:\projects\nairaland
         
          C:\projects\nairaland\src   - put MyFirstApp.java here
         
          C:\projects\nairaland\classes  - put nothing here, we will tell the javac (compiler) to put thing here for use       
                   
          C:\projects\nairaland\docs    -  nothing here, we will beg javadoc to help us too
         
Now we are done. Remember the rules, no IDE and Never compile from the editor. If you do i will know but won't tell
how. So, open the dos prompt.Go to our nairaland project folder.

         C:\projects\nairaland      - we all should be here, am right,if you are not here, please better be
                        "so thing is about to happen"
                       
Let's compile the Application. Do this.

     
     C:\projects\nairaland>javac -d classes src\MyFirstApp.java
     
     C:\projects\nairaland>     - if everything is ok, we are back here.

First thing just happend. Check the classes folder and what happened there. Please let me know.
If you missed the first please don't pass here, until you are sure you saw what happened.
If you are here, let's see another thing happening. So do this.

     
         
     C:\projects\nairaland>javadoc -d C:\projects\nairaland\docs -keywords -author -v
     ersion src\MyFirstApp.java
     
     You will see all this stuffs, don't panic, it just doing what we ask it to do.
     
     Creating destination directory: "C:\projects\nairaland\docs\"
     Loading source file C:\projects\nairaland\src\MyFirstApp.java,
     Constructing Javadoc information,
     Standard Doclet version 1.6.0-rc
     Building tree for all the packages and classes,
     Generating C:\projects\nairaland\docs\com/nairaland/\MyFirstApp.html,
     Generating C:\projects\nairaland\docs\com/nairaland/\package-frame.html,
     Generating C:\projects\nairaland\docs\com/nairaland/\package-summary.html,
     Generating C:\projects\nairaland\docs\com/nairaland/\package-tree.html,
     Generating C:\projects\nairaland\docs\constant-values.html,
     Building index for all the packages and classes,
     Generating C:\projects\nairaland\docs\overview-tree.html,
     Generating C:\projects\nairaland\docs\index-all.html,
     Generating C:\projects\nairaland\docs\deprecated-list.html,
     Building index for all classes,
     Generating C:\projects\nairaland\docs\allclasses-frame.html,
     Generating C:\projects\nairaland\docs\allclasses-noframe.html,
     Generating C:\projects\nairaland\docs\index.html,
     Generating C:\projects\nairaland\docs\help-doc.html,
     Generating C:\projects\nairaland\docs\stylesheet.css,
     
C:\projects\nairaland>  - so we are back here again.

Now go to docs folder.

     C:\projects\nairaland\docs
     
whao  where did the resources,com folders and the html file come from. Lession 2, let me know.

Finally to run MyFirstApp. Go here (dos prompt)

    C:\projects\nairaland
   
    type this command
   
   
   
    C:\projects\nairaland>java -classpath classes com/nairaland/MyFirstApp
   
    Learning Java Programming Without Tears at Nairaland.com       - So this is the result of application
   
C:\projects\nairaland>
   
Take a look at the code,documentation and all the commands (dos), figure out our they relate.
Please do this before my next post. Remember, promised to be slow.

So many things and so many guestions a guess. Q and A next.

Stunts Corner.

For people with --- never mind let's try somethings.

1.   Delete the docs and classes folders. Don't worry just do it.
2.   Run the javac command again. ie

     C:\projects\nairaland>javac -d classes src\MyFirstApp.java
     
     C:\projects\nairaland>javadoc -d C:\projects\nairaland\docs -keywords -author -version src\MyFirstApp.java
     
As you can see you can actually use the java command tools to auto generate and package our codes.
Next, i want us to look at the documentation, compare the contents with our source code (MyFirstApp.java).

Hi mimoh_mi, good initiative, I want to join your Java class. I have a PC at home not connected to the web though so how do I download the J2SE, would I be able to download it into a 256MB flash drive? I go online from cafes and the owners don’t look kindly to people downloading stuffs on their systems. Could I get the software from Ikeja?
Thanks for the time and effort you are putting into this, I have just saved this page and would print it as soon as I get home!!

java is the best thing that happened to the world of programming.
Its a world on it own.

hey, you're too good to be true. y r u doing this? i really do appreciate this. i'm studying IT in the uk. though i just started, i kind of farmiliar with java. can we do this one on one? my email is obinnaoji@hotmail.com. many many thanks

@MImoh_mi

i also reside in Lagos,  I've been have a great deal of prob getting the SDK been doing night browsing just to download the stuff at the end of the day, i don't get the file working. even right now 1:33am and still downloadind the SDK with the dowload manager just hoping it works.

I will appreciate it if i can get those resources. as soon as possible. because right now am using JVM bundle with dreamweaver to compile my codes.

I reside in Ikeja/Ketu.
Thank Man.

@ mimoh

Thanks for your training. i love java but, i just don't have the time to really learn it.
I stay i lagos and i will need a copy too. how can i get it?

Infact am lost, well please u making it difficult, u can easily break it down to the slimplest format

thanks.

It's always good to learn something using the bare basics.  That way, any "upgrades" end up being a plus.  For example, I started web dev during the "dark ages".  For the longest, I used notepad.  I remember when IDEs became the in-thing.  When asked at an interview what I used, when I told them notepad, the expression on their faces was like 

For the "notepad-like" IDEs, coding in those is okay by me.  But when you get to (at least in my field) IDEs like dreamweaver, frontpage et al, I would strongly recommend against it.  You really need to know how things come together, as opposed to producing bloated code, half of which even you as the author don't understand.  In particular, wherever I have worked, any mention of graphical IDEs results in such resumes being tossed directly into the dust bin

As for using IDE's VS not using it, it's highly recommended, that beginners NOT use an IDE. It will shield you from a lot of the basics that are supposed to help solidify your knowledge. I started with notepad myself, until I came across textpad about 6 years ago or so. Textpad is one of the best basic text editors out there. It's also a big plus that it also works will with the Java compiler and interpreter. You can compile and run your Java applications and applets right there within textpad. Even if you need to pass arguments to main(). All the shops I have worked at use IBM's websphere studio. But, most of us also have  textpad on our machines. It's just one of the best editors out there. Best of all, it's a very small "free" download that installs in about a minute. Once you've mastered the basics, and you are ready for rapid development, than you can move to an IODE A very good free IODElike eclipse will serve you well in that area.


BTW, Not sure if mimoh mentioned this already, to compile/execute your apps via textpad, make sure you install the JDK before installing textpad. Because, during installation, textpad automatically searches (it does so ONLY during installation) for the java compiler and interpreter. If it does not find it, it will not perform the necessary setup to allow you to compile/run via textpad.

One of the best sites out there that will really help is, as mentioned by mimoh, javaranch.com. There are several forum there just visit the one appropriate for you. As a long time java professional, whenever I have any questions, javaranch is the first place I post to, before even trying google. So, please bookmark it and just go there to read the questions/responses in the forum of your choice(probably the beginner forum in this case).

Hello to all. First my apology to all for the long break, but thanks
to skima, who gave me a call that my fans are growing. So I promised him
to continue. While out. i have been laying my hands on new features of Java.
From IDEs to some fantastic libraries. So today i am going to look at a fundamental
aspect of programming VARIABLES.
   Everything we ever do in any programming hangs around data. Variables are just
place holders , say we want to represent say name of employee, we must first declare
a variable to hold that name, from there we are free to manipulate it in any way within the
same program or from other programs.
   Like any other programming language, Java has it's owm ways of handling the different
type of data. What is very important to us, is knowing the types and how they are being handled
as this will enable us to chose the right type of variables to represent our data. Let me quickly
list the data types we have in Java.

   1.   Byte (byte)   ----->   8 bits   Range --------> -128 to 127
   2.   Short (short) ------>16 bits           --------> -32768 to 32767
   3.   Integer (int)  -------->32 bits        --------> -2147483648 to 2147483647
   4.   Long (long)  ---------->64 bits        --------> -9223372036854775808 to 9223372036854775808
   5.   Double (double) ------->32 bits        ------->  this is floating points (Home work, find float min and max values)
   6.   Float (float)   ------->64 bits        ------->  do same for this
   7.      Boolean (boolean)  ----> represent True or False
   8.      Character (char)   -----> used to represent single characters. (basically int under the hood) --> range 0 to 65535.
   
These are the basic data types we have in Java, they are called PRIMITIVE Data type
and each have it's own range as shown above and default values as we will see later. Why must we know the range ? Please post
your answers here. Ok, let's play with these data types.
   

// This application is to show the default values of Java primitive data types

public class VariablePlay {

   /**
    By coding standard, variable names must start with small letter.
   You must also know that the name of primitive data types are keywords
   in Java, as such you can use them to to declare your own variable, method
   or class names.
   **/

   // Here am just going to declare them, without initialisation
   // the compiler will do that for me.
   // The law say you can do this only for class variable
   // more on that later

        // things on the left are the data types and right the variable names
   byte myByte;
   short myShort;
   int myInteger;
   long myLong;
   double myDouble;
   float myFloat;
   char character;
   //Here let's add a char and initialise it
   char initChar = 100;
   boolean myBoolean;

   /**
   Let me just add a constructor, but if I don't add, the compiler will do it for \
   me. If you don't declare one, the compiler adds a default constructor for you.
   more on that later.Note same name with the class name and no return type
   **/

   public VariablePlay() {

      //Let output something here to show when this constructor is called

      System.out.println("I am VariablePlay Constructor , never mind");
   }

   //This our main method, entry method for our program

   public static void main(String []args){


      // Am just going to instantiate my class(make an object of the class and call it vp)
      VariablePlay vp = new VariablePlay();

      //use the object created ie vp to print out the default values
      System.out.println("Default Value For byte = " + vp.myByte);
      System.out.println("Default Value For short = " + vp.myShort);
      System.out.println("Default Value For Interger = " + vp.myInteger);
      System.out.println("Default Value For long = " + vp.myLong);
      System.out.println("Default Value For double = " + vp.myDouble);
                System.out.println("Default Value For float = " + vp.myFloat);
                System.out.println("Default Value For char = " + vp.character);
                System.out.println("Default Value For char = " + vp.initChar);
                System.out.println("Default Value For boolean = " + vp.myBoolean);

   }
}



Result :

I am VariablePlay Constructor , never mind
Default Value For byte = 0
Default Value For short = 0
Default Value For Interger = 0
Default Value For long = 0
Default Value For double = 0.0
Default Value For float = 0.0
Default Value For char =
Default Value For char = d
Default Value For boolean = false

Note:
1.  the first four have default values of 0. All of these are basically int
2.  The two output for char has nothing and d. char is unsigned (Can only be positive number)
3. boolean has false, used to test conditions
4. Float and double represent floating point number ie decimal
5. All numeric data type are signed in Java(ie can hold positive or negative values) except char.

For the Home work, take a look at the Java API Specification, each of these data type have a class
use them to get the maximium and minimium values of each. Just try, no matter you answer post it.

Sorry just want to cover up for the lost time, so here is my solution to the home work
I will be looking forward to other solution. Yours might just be better than mine.


// Solution to the home work
// if you haven't tried it, please do

//Notice no public in class decreation
// more on that later
class MinMax {

   /**
   *Am not going to declare any class (Instance variable)
   *because they all aready have values.
   *Take a look at the API, Notice
   *each of these primitive types have a class
   *and some static field. Static fields are Class
   *variables that it shared among mulitiple class instances.
   * I will demostrate that in the next code
   **/

   //static byte byteMin = Byte.MIN_VALUE;



   public static void main(String []args){
      /**
      *So just going to output the minimiun and maximium
      *values of all the primitive data types.
      *Notice I just use the class dot the value fields.
      * static fields for you
      **/

      System.out.println("Minimium value of byte is  "+ Byte.MIN_VALUE);
      System.out.println("Maximinm value of byte is  "+ Byte.MAX_VALUE);
      System.out.println("Minimium value of short is  "+ Short.MIN_VALUE);
      System.out.println("Minimium value of short is  "+ Short.MAX_VALUE);
      System.out.println("Minimium value of int is  "+ Integer.MIN_VALUE);
      System.out.println("Maximinm value of int is  "+ Integer.MAX_VALUE);
      System.out.println("Minimium value of long is  "+ Long.MIN_VALUE);
      System.out.println("Maximinm value of long is  "+ Long.MAX_VALUE);
      System.out.println("Minimium value of double is  "+ Double.MIN_VALUE);
      System.out.println("Maximinm value of double is  "+ Double.MAX_VALUE);
      System.out.println("Minimium value of float is  "+ Float.MIN_VALUE);
      System.out.println("Maximinm value of float is  "+ Float.MAX_VALUE);

      //Here we need to do some extra work to get the min and max value
      System.out.println("Minimium value of char is  "+ Character.MIN_VALUE);  // prints blank
      System.out.println("Maximinm value of char is  "+ Character.MAX_VALUE);  // prints ?
      System.out.println();
      System.out.println("About to do the tricks of getting the minimium and maximium values of char");

      /**
      * To print the minimiun and maximium values of char can be quite tricky
      *Remember char is just init under the hood.
      *We got the value ----> Character.MIN_VALUE
      *Passed the value to the Character.valueOf(Character.MIN_VALUE)
      *Change th result to interger (int)Character.valueOf(Character.MIN_VALUE)
      **/



      System.out.println("Minimium value of char is  "+ (int)Character.valueOf(Character.MIN_VALUE));
      System.out.println("Maximium value of char is  "+ (int)Character.valueOf(Character.MAX_VALUE));


   }
}


Result

Minimium value of byte is  -128
Maximinm value of byte is  127
Minimium value of short is  -32768
Minimium value of short is  32767
Minimium value of int is  -2147483648
Maximinm value of int is  2147483647
Minimium value of long is  -9223372036854775808
Maximinm value of long is  9223372036854775807
Minimium value of double is  4.9E-324
Maximinm value of double is  1.7976931348623157E308
Minimium value of float is  1.4E-45
Maximinm value of float is  3.4028235E38
Minimium value of char is
Maximinm value of char is  ?

About to do the tricks of getting the minimium and maximium values of char
Minimium value of char is  0
Maximium value of char is  65535