for loop without index declaration

Question

So I declare a variable some where and initialize it. Now later on I need to use it to loop while its still positive so I need to decrement it. To me looping using a condition and a decrement calls for a for but for it we are missing the first part the initialization. But I don't need to initialize anything. So how do I go about that in a nice way.

for (space = space; space > 0; space--)//my first way to do it but ide doesnt like it

Second way:

for (; space > 0; space--)//my friend recommended me this way but looks kind weird

Are there more ways for me to have a loop with only condition and increment/decrement?

P.S spell check doesn't know that "decrement" is a word. I'm pretty sure it is...

Solution 1

another way is this one:

Integer i = 10;
while(--i>0) {
    System.out.println(i);
}

When i is 0 while condition is false... so.. it will print from 9 to 1 (9 items)

Integer i = 10;
while(i-->0) {
    System.out.println(i);
}

Will print from 9 to 0... (10 items);

Solution 2

The latter way is reasonable. An alternative - if you don't have any break/continue statements - would be:

while (space > 0)
{
    // Code

    space--;
}

Comments

[Jon Skeet]

The post-decrement here will happen before the first body, so the loop will never see it in its "original" value, if you see what I mean.

[Abdullah Jibaly]

Yep, fixed accordingly. It can be useful though in the original form if you just want to make sure the condition is satisfied. Thanks for the correction.

[zetologos]

@JonSkeet But a pre-decrement would fix that. Right?

[Abdullah Jibaly]

No Jon is saying you'll never see the first value of space (if you need it).

[Jon Skeet]

@AbdullahJibaly: The way you've got it, the "..." would still never see the original value of space. The "..." needs to be before space--.

[zetologos]

Well I want the original value for the first run. So wouldn't this work while (--space > 0) ...

[Abdullah Jibaly]

No it wouldn't. Of course if you liked that approach you can change your condition to (--space >= 0) and then take that into account in your body.