From Script | Spoken-Tutorial
Jump to: navigation, search
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 these 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 (.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: public static void main parentheses inside parentheses String arg square brackets.
03:10 main function marks the starting point of the program.
03:15 We will describe public, static, void and String 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, type: System dot out dot println parentheses semicolon.
03:59 This is the statement used to print a line.
04:05 Semicolon 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 the Terminal.
04:38 Make sure that you are in the directory where you saved your ''
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 '' file present in the 'Demo' folder.
05:06 Let's compile this file. So, type: javac Space HelloWorld dot java and hit Enter.
05:21 This compiles 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 the editor.
06:22 Now, remove the semicolon 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 semicolon (;) 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 'ChessGame' 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 lowercase.
08:39 and all new words followed should begin with an uppercase.
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 summarizes 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
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.