Java/C2/while-loop/English-timed

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. [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 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' 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 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 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 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 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 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 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 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 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
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08:17	This tutorial has been contributed by TalentSprint. Thanks for joining.

Contributors and Content Editors

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