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Revision as of 12:44, 13 August 2013 by Sneha
|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
JDK 1.6 and
|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. http://spoken-tutorial.org|
|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|
|06:51||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
|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.