do...while loop

[eva]

Another quick question:

How can the following be done using do ... while loop? I hope it wont affect the efficiency of the program.

Code:

                int i=0;
		
		while(i<21)
		{
			System.out.println(i);
			i++;
		}

[kureikougaiji]

i=0;

do{

System.out.println(i);
i++

}
while(i<21);

output:
0
1
2
.
.
.
21

it printed 21 before checking it...

[tim]

Hello

You should add an extra check, since the condition for the do-while loop is at the end of the loop statement.

Code:

int i=0;
do{
   if (i < 21) System.out.println(i);
   i++;
}
while(i<21);

Gives the output

Code:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

[felixtfelix]

Eva,
We can do this in even simple way
int i=0;
do{
System.out.println(i);
}while(++i<21);

[Eranga]

[quote=tim;13228]

Code:

int i=0;
do{
   if (i < 21) System.out.println(i);
   i++;
}
while(i<21);

tim, why you use 'if' statement there. Because both 'if' and 'while' conditions are do the same.

[Eranga]

Quote:

Originally Posted by kureikougaiji

it printed 21 before checking it...

Are you sure? It doesn't print 21 actually. Go through the code again. By the way, you don't have define the variable type of 'i'.

[tim]

Hello Eranga

I assumed that what kureikougaiji said, was correct. I've compiled and ran the code and 21 was not printed. The if-statement is unnecessary.

Thank you.

[Eranga]

No tim,

Just I'm worried there is any special reason to use that.

[shasaf]

Hi Eranga,

Basically what tim is trying to tell you is that the condition {i<21} in a do-while loop comes up at the end. What happens in this case is for the first time there is no condition to check and the data will get printed in any case. Only after the printing of data will the condition be checked. For instance if you had initiated i to 24 to start off, the piece of code without the if condition will print 24, and then check the condition. Hence only 24 will get printed. Infact the basic purpose of a do while loop is when you are sure that the piece of code has to get executed at least once.

[tim]

Welcome to the forums shasaf.

You've got it spot on. That was exactly what I indented.

[kureikougaiji]

fighting over simple stuffs...

[tim]

Hello kureikougaiji.

We do not fight on the forums. It is a place to learn and improve. I admitted my mistake and there is no reason to fight.

I usually use an if statement in these situations to prevent logical errors, since algorithms are not always this simple. In my point of view- better safe than sorry.

[kureikougaiji]

yes, you're all right you know.. in programming, there is a vast ways on how to implement a problem.. sorry if i'm using the wrong words earlier.. peace..

[kureikougaiji]

wrong grammarrrr

[eva]

Thanks for the discussion on different possibilities. Yes, Its a learning place where we improve our skills.

- PEACE

[Eranga]

Quote:

Originally Posted by shasaf

What happens in this case is for the first time there is no condition to check and the data will get printed in any case.

First of all, welcome to the forum.

Yes, you are right. But the reason is this. Normally in use of do-while loop is, do the processing first and then check the condition fired or not. If you want to check the condition first, you can use either 'if' or 'for' loops in different ways. I telling this is the normal practice I do, as well as most of the people.

[Eranga]

Quote:

Originally Posted by tim

Hello kureikougaiji.

We do not fight on the forums. It is a place to learn and improve. I admitted my mistake and there is no reason to fight.

I usually use an if statement in these situations to prevent logical errors, since algorithms are not always this simple. In my point of view- better safe than sorry.

Yes tim. Our community is the best place to learn and improved our knowledge. And also, regarding your coding practice, different people have there own methods to do it in safely. As you said, the way you explain is safe for you