Thread: Situations for using while loops, do while loops, and for while loops.

while loops are great for when you don't know how many times the program will run, right?

For example, a program that asks the user to do some calculation, then asks him/her to press 0 to quit. (am i right here?)

do while loops are executed once, and are useful for data validation right? Can you possibly give a scenario/example of this?

and for while loops are good for when you know the actual quantity or number of times you need to check something, right? Can someone give a scenario of this please?

DO-WHILE

do
{
statements;
}while (condition);

As the while loop, it can be counter-controlled or sentinel- controlled.
The body of the loop continues to execute as long as the condition is true or until the condition becomes false.
Any variables declared inside the do-while belongs to the do-while only.
The condition has to become false sooner or later; otherwise, it’s an infinite loop.

*This is a good loop to use with log-ins, with menus (list of options), or when you need to force the user into a loop*


WHILE

while is a pre-test loop that requires testing of the condition in the while header before the body of the loop is entered.

while(condition)
{
statements;
}

The condition (also referred to as the test expression) tests the value in the variable that controls whether the loop continues or stops, aka, loop-control variable.

*This is a good loop to use for testing the validity of input data.*

Thanks, what about the FOR loop, isn't that useful as well? when you know the actual amount of times you need to check something? because of that simple part in the loop where you can easily incremement something?

for example: for(i = 0; i <= 10; i++)//this will execute 10 times
{
System.out.println(i);
}

The best way to understand looping and the utility of each loop is to use them. Write a simple study program that does something mutiplie times, and complete the task using each kind of loop. That darned ascii art, pyramids and other things out of asterisks, is an excellent loop exercise and time waster.

Thank you GregBrannon, not quite sure I know what you're talking about (ascii art, pyramid) Sorry. I'm still kind of new to forums so I don't really know how to navigate them that well. But thankfully I found out about this forum because everyone here has been really great

Here's an example of an ASCII Art problem from "C: How to Program, 6th Edition," Deitel.

4.16 (Triangle Printing Program) Write a program that prints the following patterns separately, one below the other. Use for loops to generate the patterns. All asterisks should be printed by a single printf statement of the form printf( "*" ); (this causes the asterisks to print side by side). [Hint: The last two patterns require that each line begin with an appropriate number of blanks.]

(A)
 *
 **
 ***
 ****
 *****
 ******
 *******
 ********
 *********
 **********
 
 (B)
  **********
  *********
  ********
  *******
  ******
  *****
  ****
  ***
  **
  *
 
 (C)
  **********
   *********
    ********
     *******
      ******
       *****
        ****
         ***
          **
           *
 
 (D)
          *
         **
        ***
       ****
      *****
     ******
    *******
   ********
  *********
 **********
 
Extra credit:
 
    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

Originally Posted by GregBrannon

Here's an example of an ASCII Art problem from "C: How to Program, 6th Edition," Deitel.

4.16 (Triangle Printing Program) Write a program that prints the following patterns separately, one below the other. Use for loops to generate the patterns. All asterisks should be printed by a single printf statement of the form printf( "*" ); (this causes the asterisks to print side by side). [Hint: The last two patterns require that each line begin with an appropriate number of blanks.]

(A)
 *
 **
 ***
 ****
 *****
 ******
 *******
 ********
 *********
 **********
 
 (B)
  **********
  *********
  ********
  *******
  ******
  *****
  ****
  ***
  **
  *
 
 (C)
  **********
   *********
    ********
     *******
      ******
       *****
        ****
         ***
          **
           *
 
 (D)
          *
         **
        ***
       ****
      *****
     ******
    *******
   ********
  *********
 **********
 
Extra credit:
 
    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

Hi Greg, could you please see my code located here: http://www.javaprogrammingforums.com...umns-form.html

I have to do something similar to this, and my code is listed there as well.