Difference between revisions of "Java/C2/First-Java-Program/English-timed"
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Revision as of 16:30, 3 June 2014
| Time' | Narration |
| 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 |
| 00:23 | Here we are using Ubuntu version 11.10 and 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 | so Save 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.
|
| 02:53 | So type: |
| 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. |
| 04:05 | 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's go to 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 |
| 04:56 | ls, press 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 | So After successful compilation, run the program using the command, |
| 05:56 | java (This time no c) space HelloWorld (and 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 to save the file before compiling |
| 07:22 | Let us go back to the Terminal. |
| 07:25 | Compile the file using javac 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 | * The 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 | For Example: showString(), main(), goToHelp(). Here s of show is in lowercase while S of string is in uppercase
|
| 09:02 | 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 print 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 [1] |
| 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 to those who pass an online test |
| 10:17 | For more details, please write to contact@spoken-tutorial.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
[2]
|
| 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. |
Contributors and Content Editors
Arya Ratish, Ashwini, Gaurav, Kavita salve, PoojaMoolya, Pratik kamble, Priyacst, Sandhya.np14, Sneha, Vasudeva ahitanal
