From Script | Spoken-Tutorial
Revision as of 09:50, 28 May 2013 by Sneha
|00:02||Welcome to the Spoken Tutorial on getting started with the First java program.|
|00:09||In this tutorial we will learn|
|00:11||To create a simple java program.|
|00:14||To compile the program.|
|00:16||To run the program. and|
|00:19||About the naming conventions followed in java|
|00:24|| Here we are using Ubuntu version 11.10 and Java Development Environment jdk 1.6
|00:32||To follow this tutorial JDK 1.6 must be installed on your system.|
|00:39||If not, for relevant tutorial please visit our website which is as shown.|
|00:46||Alright now Let us write our first java program.|
|00:51||For that you need a Terminal and you need a Text Editor.
|00:56||I am using gedit as my Text Editor|
|01:01||In the text editor, we will first create the class HelloWorld.|
|01:06||So type class HelloWorld HelloWorld is the name of the class.
|01:17|| And Open curly bracket. Enter and close curly bracket.
|01:24||The code between this two curly brackets will belong to the class HelloWorld|
|01:33||Now save the file by clicking on Save icon at the top|
|01:37||It is a good practice to save the file frequently.|
|01:43||soSave As Dialog box appears.|
|01:46||Browse the location where you want to save your file.|
|01:51||Here, in the home directory i will create a folder.|
|01:57||Let us name it Demo and press enter|
|02:02||Then inside this folder we will save the file.|
|02:08||In the Name text-box, type the name of the class.|
|02:13||In java, the name of the class and the file name should be same.|
|02:20||Recall that we created class HelloWorld.
|02:25||So we will save the file as HelloWorld dot java|
|02:33||Dot java is the file extension given to the java file.|
|02:39||Then click on Save button. So the file is now saved.|
|02:47|| Inside the class, we write the main method.
|02:54||public static void main parentheses inside parentheses String arg Square brackets
|03:10||Main functions marks the starting point of the program.
|03:15||We will describe public, static, void and String arg in a future tutorial.
|03:23||Then once again, open curly bracket.|
|03:27||Press Enter and close curly bracket.
|03:32||The code between these two curly brackets will belong to the main method.|
|03:41|| We will now write a code to display a line on the Terminal.
|03:46||So inside main method typeSystem dot out dot println parentheses semi-colon
|03:59||This is the statement used to print a line. semi-colon is used to terminate a line.
|04:10||Now let us tell Java what to print.
|04:13||So Within parentheses in double quotes type My first java program exclamation mark.|
|04:30||Let us Save the file by clicking on Save icon.|
|04:36||Let us go to the Terminal.|
|04:38|| Make sure that you are in the directory where you save your HelloWorld.java
|04:46||Remember that I am in my home directory.
|04:50||So type cd Space Demo and hit Enter
|04:59||We see HelloWorld.java file present in the Demo folder.|
|05:06|| Lets compile this file so type javac Space HelloWorld dot java and hit enter
|05:21||This compile the file that we have created.|
|05:25||Alright now the file is compiled as we see no error.|
|05:30||We can see HelloWorld.class file created.|
|05:36||This file can run anywhere.|
|05:38||That is, on any Operating System.|
|05:41||We do not need java compiler as well.|
|05:45||Hence, java is rightly described as “write once, run anywhere.”
|05:51||After successful compilation, run the program using the command,|
|05:56||java (no c) space HelloWorld (no dot java) extension and hit Enter.|
|06:07||You will get the output My first java program!|
|06:13||So we have written our first java program.Let us go back to editor
|06:22||Now, remove the semi-colon which is at the end of the statement.|
|06:27||Click on Save icon.|
|06:29||Let us go back to the Terminal.|
|06:33||Run the command javac HelloWorld dot java.|
|06:41||The compiler gives an error.|
|06:44||It says, a semi colon is expected on the fifth line.
|06:52||The up arrow points to the error statement.|
|06:57||Let us go back to the Editor.|
|07:01||In Java, all statements are terminated with semicolons.|
|07:06|| So go to the fifth line and add a semicolon.
|07:13||Click on the Save icon. It is necessary tosave the file before compiling|
|07:22||Let us go back to the Terminal.|
|07:25||Compile the file using javac Space HelloWorld dot java.|
|07:32||The file is successfully compiled as we see no errors.|
|07:36||Now, run the program using the command java HelloWorld and .
|07:45||We see the output My first java program!|
|07:49||This is how you handle errors in java.|
|07:54||As the series progresses, we will learn more about the errors.|
|08:02||We now see what are the naming conventions in java.|
|08:06||* class name should be in CamelCase.|
|08:10||* Which means each new word begins with an upper case.|
|08:14||* Example: class HelloWorld, class ChessGame.|
|08:19||So, H of hello and W of World are in uppercase.
|08:25||Similarly C and G of Chess and Game respectively are in uppercase.|
|08:31||The method name should be the mixed case.|
|08:35||Which means that the first word should begin with a lower case.|
|08:39||And all new words followed should begin with an upper case.|
|08:44||Also the method name should be a verb.
|08:48|| 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.|
|09:06||We cannot use keywords for our class, method or variable name.|
|09:13||For example: cannot use keywords like public, private, void, static and many more.
|09:22||So in this tutorial, we have learnt to write, compile and run a simple java program.|
|09:30||We also saw the naming conventions followed in java.|
|09:35|| For self assessment write a simple java program to prints Java file name and class name should be same.
|09:47||To know more about the Spoken Tutorial Project|
|09:50||Watch the video available at http://spoken-tutorial.org/What_is_a_Spoken_Tutorial|
|09:58||It summarises the Spoken Tutorial project|
|10:02|| If you do not have good bandwidth, you can download and watch it
|10:08||The Spoken Tutorial Project Team|
|10:10||Conducts workshops using spoken tutorials|
|10:13||Gives certificates for those who pass an online test|
|10:17|| For more details, please write to firstname.lastname@example.org
|10:25||Spoken Tutorial Project is a part of the Talk to a Teacher project|
|10:30||It is supported by the National Mission on Education through ICT, MHRD, Government of India|
|10:38|| More information on this Mission is available at
|10:49||We have come to the end of this tutorial.|
|10:51||Thanks for joining.|
|10:53||This is Prathamesh Salunke signing off. Jai Hind.|