While or For loop which one suits for which condition

Question

Some iteration code is written like this

while(true)                           for(int i = 0 ; i<=4;++i)
                                        {
{  
    System.out.println(i);               System.out.println(i);
   if(i==4)                                
     break;
                                          }
}

both have the same logic inside it take it as assumption. So which one will be faster, better to use in code and what are the implication of using any one of it??

@DeepSaxena then update your post so that it will be benefit for the new visitors — SpringLearner, Oct 18 '13 at 11:01
The best to use in code is the one which corresponds to the coding conventions where you are programming. — James Kanze, Oct 18 '13 at 11:38

Ferenc Deak · Answer 1 · 2013-10-18T11:31:08.137

1

The first one is an endless loop :) (depending on the i before the loop) The second one does (almost) what you expect. Go grab a good manual about your programming language, it will explain the difference.

On another level: Loop optimizations are much better suited to for loops (AFAIK) so a "clever" compiler might generate better code for the "for" loop. http://en.wikipedia.org/wiki/Loop_optimization

edited Oct 18 '13 at 11:31

answered Oct 18 '13 at 10:56

Ferenc Deak

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sry i forgot to mention ++i in while loop – Deep Saxena Oct 18 '13 at 11:00
My comment is still valid: go grab a manual :) – Ferenc Deak Oct 18 '13 at 11:01
3

**go grab a manual** if you want to answer then answer it completely so that future users will be benefited .By giving only Partial answers will be better in comment section – SpringLearner Oct 18 '13 at 11:04

score 0 · Answer 2 · answered Oct 18 '13 at 10:57

They are totally different, but if their behavior was the same, never use break; in such situations.

The second bucle is more clear, when you have to take into consideration performance, you don't have to do it in retreat of clean code.

The second bucle is self-documented while the first you need to add a reason to add the break in order to be understandable.

score 0 · Answer 3 · answered Oct 18 '13 at 10:58

0

to end the while loop on the left you have to incriment i

EDIT : Assuming i is less that 4 when the loop starts

answered Oct 18 '13 at 10:58

sukhvir

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score 0 · Answer 4 · answered Oct 18 '13 at 11:01

0

For that purpose, use a for one, since you need the value of i. It is more understanding for maintenance. Anyway, the compiler will optimize both codes and runtime may be the same.

answered Oct 18 '13 at 11:01

Didac Perez Parera

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score 0 · Answer 5 · answered Oct 18 '13 at 11:04

Considering your while is not an infinite loop there is no difference as far as performance is concerned. However, I personally prefer for loop as it is cleaner. Consider this:

int i = 0;
while (true) {
  doSomething(i++);
  if (i == 4)
    break;
}

which looks cleaner with

for (int i = 0; i <= 4; i++)
  doSomething(i);

score 0 · Answer 6 · answered Oct 18 '13 at 11:10

0

Im using for whenever I know the number of itterations in advance.

answered Oct 18 '13 at 11:10

FeinesFabi

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score 0 · Answer 7 · answered Oct 18 '13 at 11:10

If you know how many time you want to do some operation you have to use for loop otherwise use while loop. For example:

If you have some array or arraylist then suppose you want to add all elemnts of it then you should use for loop because you know size of arraylist by size() function and know the size of array by length attribute.
If you have resultset and you want to retrieve all rows from it then you should use while loop because you don't know how many element in resultset object.

score 0 · Answer 8 · answered Oct 18 '13 at 11:30

Neglecting the typo of your question,Assuming that you want to know which one i choose when Both loops are essentially doing the same thing.

The answer is you can go for any one.

But it's better to use for loop if you know how many times you want to run a loop as you can set the condition during initialization. And in future also it will be easy to change it if you want to extend the iteration.

You can prefer while if you are not sure for how much iteration you want. In your case i will go with for loop

Note: the answer is opinion based.

While or For loop which one suits for which condition

8 Answers8