Difference between revisions of "Java/C2/First-Java-Program/English-timed"

|| '''Time''''

|| In this tutorial we will learn  

| To create a simple java program.  

| To compile the program.

| To run the program.  and

| About the naming conventions followed in java

|  Here we are using   Ubuntu version 11.10 and   jdk 1.6

 

 

|  To follow this tutorial '''JDK 1.6 '''must be installed on your system.

|If not, for relevant tutorial please visit our website which is as shown.

|Alright now let us   write our first java program.

|For that you need a '''Terminal''' and you need  a '''Text''' '''Editor'''.

 

 

 

| I am using '''gedit''' as my '''Text Editor'''  

|  In the '''text editor'''   , we will first create the class '''HelloWorld'''.  

|So type '''class HelloWorld'''. '''HelloWorld '''is the name of the class.

 

| And   Open ''curly bracket''.   '''Enter '''and close ''curly bracket''.

 

 

 

|  The code between this two curly brackets  will belong to the class '''HelloWorld'''

|  Now save the file by clicking on '''Save '''icon at the top  

|  so '''Save As Dialog box ''' appears.

|  Here, in the home directory i will create a folder.

|Let us name it   '''Demo''' and press ''' enter'''

|Then inside this folder we will save the file.

| In the '''Name''' text-box, type the name of the class.

|In java, the name of the class and the file name should be same.

|Recall that we   created  class   HelloWorld.

 

|So we will save the file   as''' HelloWorld dot java'''

|  '''Dot '''java is the file extension  given to the java file.

|  Then click on '''Save '''button. So the file is now saved.

| Inside the class, we write the '''main''' method.  

 

|So type:

 

|'''''public static void main '''  ''parentheses'' inside  ''parentheses'' '''String''' '''arg''' Square brackets''

 

|'''Main''' functions marks the starting point of the program.

 

|We will describe '''public, static, void and String arg''' in a future tutorial.

 

|Then  once again, open curly bracket.

|Press '''Enter '''and close curly bracket.

 

 

 

|  The code between these two curly brackets will belong to the main method.

|So inside main method type'''''System '''dot''' out '''dot''' println''''' parentheses semi-colon

 

|This is the statement used to print a line.   

|semi-colon is used to terminate a line.

 

|Now let us tell Java, what to print.

 

| So Within '''''parentheses in double quotes type, My first java program exclamation mark'''.''

|  Let us '''Save '''the file by clicking on '''Save''' icon.

|  Let's go   to '''Terminal'''.

| Make sure that you are in the directory where  you save your  '''HelloWorld.java'''

 

|Remember that I am in my home directory.

 

|-

|So''''' '''''type''''' cd '''Space''' Demo '''''and''''' '''hit''' Enter'''''

|ls, press Enter.

|We see  ''' HelloWorld.java''' file present in the Demo folder.

| Lets compile this file so type   '''javac '''Space''' HelloWorld '''dot''' java''''' and hit''' enter'''  

 

|This   compile the file that we have created.  

|  Alright now the file is compiled as we see no error.

|This file can run anywhere.

|That is, on any '''Operating System. '''

| So After successful compilation, run the program using the command,  

|'''''java '''''(This time no c) space '''''HelloWorld '''''(and no dot java extension) and hit '''Enter'''.

| You  will get the output '''My first java program!'''

|So we have written our first java program.Let us go back to '''editor'''

|  Now, remove the '''''semi-colon '''''which is at the end of the statement.

|   Click on     '''Save''' icon.

| Let us go back to the '''Terminal'''.

|  Run the command '''''javac ''' ''' HelloWorld '''dot''' java'''''.  

|It says, a semi colon is expected on the fifth line.

 

|The up arrow points to the error statement.

|  Let us go back to the ''' Editor'''.

|     07:06

| So go to the fifth line and add a semicolon.

 

|  Click on the '''Save '''icon. It is necessary to save the file before compiling

|Compile the file using   '''''javac ''' ''' HelloWorld '''dot''' java'''''.  

|   The file is successfully compiled as we see no errors.

|Now, run the program using the command '''''java'''''  '''''HelloWorld''''' and  .

 

| We see the output '''My first java program!'''

|This is how you handle errors in java.

|*  The class name should be in CamelCase.

|* Which means each new word begins with an upper case.

|* Example: class HelloWorld, class ChessGame.

|So,''' H''' of hello and  '''W''' of World are in uppercase.

 

|Similarly C and G of Chess and Game respectively are in uppercase.  

|  The method name should be the mixed case.

| Which means that the first word should begin with a lower case.  

|And all new words followed should begin with an upper case.

|Also the method name should be a verb.

 

 

|  For   Example: showString(), main(), goToHelp(). Here '''s''' of show is in lowercase while '''S''' of string is in uppercase  

 

|The variable name should not begin with '''digits''' .  

| We cannot use keywords for our class, method or variable name.

|For example:  cannot use keywords like''' public, private, void, static and many more'''.  

 

 

|  So in this tutorial, we have learnt to write, compile and run a simple java program.

| | For self assessment write a simple java program to print '''Java file name and class name should be same'''.

 

|To know more about the Spoken Tutorial Project

|  Watch the video available at [http://spoken-tutorial.org/What_is_a_Spoken_Tutorial]  

| It summarises the Spoken Tutorial project  

| If you do not have good bandwidth, you can download and watch it  

|  The Spoken Tutorial Project Team

| Conducts workshops using spoken tutorials  

|Gives certificates to those who pass an online test  

|  Spoken Tutorial Project is a part of the Talk to a Teacher project  

|It is supported by the National Mission on Education through ICT, MHRD, Government of India  

| More information on this Mission is available at  

 

[http://spoken-tutorial.org/NMEICT-Intro]  

 

 

|This is Prathamesh Salunke signing off.  Jai Hind.