Double-condition while

Question

What does the following statement mean in Java?

while(condition_1) {
    do something...
} while (condition_2);

Is there any real-world situation to use it?

UPDATE: code example

    int i = 3;
    while (i < 10) {
        System.out.println(i++);
    } while (i < 15);

Please show compilable code when asking about code. Or start comments in front of `do something ...` — Sotirios Delimanolis, Jan 08 '14 at 19:12
That looks like an infinite loop to me... The value of `i` never changes after breaking out of the first while loop. This question is senseless in its current state. — jahroy, Jan 08 '14 at 19:15
So many downvoters while person just want to understand what it used for. How you can ask the real code sample if he asks for **"Is there any real-world situation to use it?"** What if he asked about "foreach" purpose? Did you ask then for real code too? — Kosmo零, Jan 08 '14 at 19:21
just several statements formatted badly, its just two while-s man — anfy2002us, Jan 08 '14 at 19:24
@kosmos - One code sample does not compile. The other is an infinite loop. — jahroy, Jan 08 '14 at 19:25
@jahroy - He just wanted to understand what that statement means. I guess he don't know that you can write even single line code, so he got confused, but others started to ask for real code, which is impossible to show for non existent "rare" double while statement. — Kosmo零, Jan 08 '14 at 19:35
@anfy2002us - Maybe this is just kind of programming task where teaches asked him to explain what this code does. — Kosmo零, Jan 08 '14 at 19:41

score 10 · Answer 1 · answered Jan 08 '14 at 19:13

10

It's just 2 while statements. There is no significance to the second while being on the same line as the closing bracket of the first while loop. Whitespace, for the most part, doesn't matter. Your code would do the same thing if there were blank lines between the two while statements.

Edit: since you edited your code to include an empty while loop, you should notice that your second while loop doesn't actually do anything other than loop. So if you loop once, you'll be looping forever. You might be confusing this with a do-while loop, in which case you should consult the tutorials: http://docs.oracle.com/javase/tutorial/java/nutsandbolts/while.html

answered Jan 08 '14 at 19:13

Kevin Workman

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So it prints 3, 4, 5, 6, 7, 8 and 9, and then iterates forever. – Amir Pashazadeh Jan 08 '14 at 19:15
Completely right explanation it seems. Also, I feel this is mostly bad practice. Why have a while that does not do anything except maybe through inside the parenthesis. OP should have posted real code. – Menelaos Jan 08 '14 at 19:17

score 2 · Answer 2 · answered Jan 08 '14 at 19:29

2

It doesn't looks for me any different from:

int i = 3;
while (i < 10) //loop that ends once i == 10
    System.out.println(i++);

while (i < 15) //infinite loop
    ; //that does nothing

There are just two while loops and badly formatted code.

answered Jan 08 '14 at 19:29

Kosmo零

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score 1 · Accepted Answer · edited May 23 '17 at 12:22

1

your second while is making your code sample to go in an infinite loop. for better understanding of do-while please go through the example mentioned here : Java do while, while

edited May 23 '17 at 12:22

Community

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answered Jan 08 '14 at 19:17

Ashish

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Double-condition while

3 Answers3