From Script | Spoken-Tutorial
Revision as of 12:44, 13 August 2013 by Sneha (Talk | contribs)

Jump to: navigation, search
Time' Narration
00:02 Welcome to the spoken tutorial on While Loop in java.
00:06 In this tutorial, you will learn About the while loop.

How To use it.

00:12 For this tutorial we are using

Ubuntu 11.10,

JDK 1.6 and

Eclipse 3.7

00:21 To follow this tutorial, you must have knowledge of relational operators in Java

00:26 If not, for relevant tutorials please visit our website as shown.
00:36 Here is the structure of a while loop.
00:39 It has two parts.
00:41 One is the loop running condition and the second is the loop variable.

00:48 Let us now look at an example. Switch to Eclipse
00:55 Here We have the eclipse IDE and the skeleton required for rest of the code

01:00 I have created a class WhileDemo and added the main method to it.
01:05 We shall print numbers from 1 to 10 using a while loop. Type int n = 1

01:15 This variable n is going to be our loop variable
01:21 type while 'in parenthesis n less than or equal to 10 open and close braces
01:33 This condition is called looping running condition.

01:37 It means the loop will run as long as this condition is true.

01:42 In our case, it will run as long as the value of n is less than or equal to 10.

01:47 And it will stop only when the value of n become greater than 10.
01:53 Inside the loop, we shall print the value of n
01:58 System.out.println(n); and then increment n = n + 1;

02:12 This way, first 1 is printed and then the value of n becomes 2.
02:18 Then the loop condition is checked.

02:21 Since it is true. 2 is printed and n becomes 3.
02:25 And so on loop progresses untill 10 is printed after that n becomes 11 and the condition is not true and the loop will stop

02:37 So Let us see the code in action.
02:39 Save and run.
02:47 As we can see, the numbers from 1 to 10 are printed.

02:52 Now we shall print numbers from 50 to 40
02:58 So We start with 50. Change n = 1 to n = 50
03:03 And We go till 40.

03:05 In other words as long as n is greater than or equal to 40. So change the condition to n greater than or equal to 40.

03:16 And since we are looping from a bigger number to a smaller number, we have decrement the loop variable.

03:22 So Change n=n + 1 to n=n - 1

03:27 Save and run. As we can see, the the numbers 50 to 40 have been printed
03:42 Now we shall print the first 10 multiples of 7.
03:48 To do that, we start with 7

03:50 So change n = 50 to n = 7and then end with 70.

03:57 Change the condition to n less than equal to 70

04:03 This way, we make sure the loop stops at 70.
04:07 To get the multiples, we shall increment the loop variable by 7.

04:12 So, change n=n - 1 to n=n + 7

04:18 This way first 7 is printed and then n becomes 14, 14 is printed and so on untill 70. Save and run
04:33 As we can see, the first 10 multiples of 7 are printed.

04:43 We can also use a while loop to get the sum of digits of a number.

04:47 Let us see how to do so.
04:49 First clear the main method.

04:54 int n equal to 13876. This is the number
05:02 Then int dSum equal to 0The variable dsum with symbolic for digit sum will contain the sum of digits

05:18 Type while, n greater than 0 open close parenthesis

05:27 The reason for using this condition will be evident in a while.
05:32 To get the sum of digits, we must first get the digits.
05:36 To do that we use modulo operator.

05:40 Type dSum = dSum + (n % 10) So we get the unit digit and add it to dsum
05:52 After that we remove the digit by dividing by 10. n = n / 10
06:08 So when the loop is run for the first time, dSum will be 6 and n will be 1387.
06:15 And when the loop is run for the the second time, dSum will be sum of 7 and 6 which is 13, and n will become 138.

06:22 So on, as the loop progresses, the digits will be removed from n and finally
06:28 n become zero.After that the condition n greater than 0 will be false and the loop will stop
06:36 So let us now add a print statement
06:42 System.out.println(dSum)
06:51 Let us see the code and action. Save and run
06:59 As we can see the sum of digit which is 25 has been printed
07:06 This way, a while loop, which is one of the most fundamental constructs in programming, can be used.
07:16 This brings us to the end of the tutorial.

07:20 In this tutorial we have learnt
  • About while loop
  • how to use it

07:26 As an assignment for this tutorial solve the following problem.

07:29 Given a number, compute its reverse by using a while loop. Example: 19435 => 53491
07:37 To know more about the Spoken Tutorial project, watch the video available at the following link, that summarizes the Spoken Tutorial project
07:45 If you do not have good bandwidth, you can download and watch it.
07:50 The Spoken Tutorial Project Team, Conducts workshops using spoken tutorials, Gives certificates for those who pass an online test
07:57 For more details, please write to contact AT spoken HYPHEN tutorial DOT org.
08:03 Spoken Tutorial Project is a part of the Talk to a Teacher project.
08:07 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
08:12 More information on this Mission is available at the following link
08:17 This tutorial has been contributed by TalentSprint. Thanks for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14, Sneha