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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 and 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. [1]
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 the 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 loop 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' becomes greater than 10.
01:53 Inside the loop, we shall print the value of 'n'.
01:58 System.out.println(n); and then increment it 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 until 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 decremented the loop variable.
03:22 So Change n=n+1 to n=n-1.
03:27 Save and run. As we can see, the numbers from 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 = 7 and then we end with 70.
03:57 Change the condition to n less than or equal to 70.
04:03 This way, we make sure that 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 until 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 0. The variable dsum which is symbolic for digit sum will contain the sum of digits.
05:18 Type: while n greater than 0 open close parentheses.
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 the modulo operator.
05:40 Type: dSum = dSum + (n % 10) So, we get the unit's 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 become 1387.
06:15 And when the loop is run for the second time, dSum will be sum of 7 and 6 which is 13 and 'n' will become 138.
06:22 And so on as the loop progresses, the digits will be removed from n and finally
06:28 n becomes 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 in action. Save and run.
06:59 As we can see, the sum of digits 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 learned: 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. It summarizes the Spoken Tutorial project.
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07:57 For more details, please write to contact@spoken-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