Difference between revisions of "Java/C2/do-while/English-timed"

|| ''Time'''

| Welcome to the spoken tutorial on''' do-while Loop '''in java'''.'''

| | In this tutorial, you will learn about

 

* '' do-while loop and'''

* '''how to use it'''

 

 

| For this tutorial we are using  

 

'''Ubuntu 11.10''',

 

|   To follow this tutorial, you musthave knowledge of''' while loop in java.'''

 

|If not, for relevant tutorials please visit our website as shown.

 

|   Here is the structure for  do-while loop.  

 

|Notice that it is similar to a while loop.

 

|First is the loop running condition. And the second is the loop variable

|And so the condition is checked after the execution of the statements inside the do block

 

|Now let us see an example.

| Switch to eclipse  

|   Here we have Eclipse IDE and the skeleton required for the rest of the code.

 

|We have created a class '''DoWhileDemo''' and added the main method to it.

 

 

 

| We are going to print the numbers from 1 to 10 using a do-while loop.

 

|Type

 

|'''int n ''equalto'' 1  '''''

 

|n is going to be   loop variable.

| then type '''do '''

|'''open  and close  braces'''

|Inside the braces'''System.out.println(n);'''

|We shall print the value of n and then increment it. '''n ''equalto'' n ''plus'' 1;'''

|'''n''''' is less than or equal to '''''10'''

 

| Outside the braces Type '''while in paranthesis(n ''less than equalto'' 10)'''

|  And close the do-while using a semi-colon

|Save and Run.

| | We see that, the numbers from 1 to 10 are printed.

|  now  Let us understand how the code is executed.

|  First, the value 1 is printed and then n becomes 2.

 

|since it is true, again 2 is printed and n becomes 3.

 

|And so on till all the 10 numbers are printed and the value of n becomes 11.

 

|  Now Let us print numbers from 50 to 40 in decreasing order.

|   So we start with 50.

|Change n = 1 to n = 50.

|  Since we are looping from a bigger number to a smaller number, we decrement the loop variable.

 

|So Change '''n = n + 1''' to '''n = n - 1'''

|  We loop as long as n is greater than or equal to 40.

 

| So Change the condition to n >= 40

|Save and Run.

|  Now let us try a different logic using the do-while loop.

|  |First Clear the main method.

|ThenType '''int n = 25;'''

| We shall see if the value in n is a perfect square or not.

|   Then type'''int x = 0;'''

 

|We shall use x to store the square root of the number if it   is a perfect square.

|   Then Type '''do'''

 

|Open and close braces.

|Inside the braces'''x '''''equal to '''''x '''''plus''''' 1'''

| And outside the braces  

 

|'''while in paranthesis (x ''into  '' x <  n)'''

 

|And Close the do-while usinga semi-colon

|  | As long a '''x '''''into '''''x '''is less than '''n''', we keep incrementing the value of x.

|  So when the loop stops, the reverse of this condition will be true.

| Which means either x into x must be equal to n.

 

|Or it  must be greater than n.

|  If '''x '''''into '''''x''' is equal to '''n''', the number is a perfect square.

 

|If it is not equal to n, the number is not a perfect square.

| '''System.out.println(x * x == n);'''

|   '''Save''' and '''Run'''.  As we can see, the output is '''true'''

 

|Let us try with other perfect square.

|   '''Change n = 25 to n = 49'''

| Save and Run

|We see that we get the  true again .

| Change 49 to 23. Save and Run and

 

|We get a false as expected.

 

|Now let us see what happens when the value of '''n''' is 0.

| Change n = 23 to n = 0 Since 0 is not a natural number, we must get a false.

 

|Let us run the code.

|Save and Run.

| We see that we get false as expected.

| This happens because even before the condition

|'''x''' ''into''''' x''' ''is less than '''''n '''is checked, the value of x is incremented and it becomes 1

 

|The loop condition fails and loop does not run.

| This way, by using a do-while loop, we make sure that 0 is not considered as a perfect square.

|   This way, a do-while loop is used for solving a range of problems.

|Specially, when the loop must run at least once.

|   This brings us to the end of the tutorial.

 

|In this tutorial, we learnt about the

| The do-while loop and how to use it

|Given a binary number, find out its decimal equivalent. Example: '''11010 => 26'''

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