Replace for-each loop with lambda expression

Question

I'm just refactoring some of my old projects to use features of Java 8.

int counter = 1;
for (Checker checker : checkers) {
    if (counter < checkers.size()) {
        checker.setNextChecker(checkers.get(counter++));
    }
}

Here's kinda Chain of Resp pattern. And I need to set next checker for every checker in the list, excluding the last one.

Still can't find the way to use Stream API here :)

I would leave it with a for loop. Better readable and I see no advantage of streams here. — lexicore
– lexicore, Commented Apr 24, 2018 at 19:02
@lexicore is this any better in terms of readability stackoverflow.com/questions/50006972/… ? — Ousmane D.
– Ousmane D., Commented Apr 24, 2018 at 21:23
@Aominè I really don't see why it should be better than a simple for-loop. — lexicore
– lexicore, Commented Apr 24, 2018 at 21:28
@lexicore good shout, I guess I was more focused on using streams as the OP requested for it. — Ousmane D.
– Ousmane D., Commented Apr 24, 2018 at 21:30
@Aominè You're absolutely correct, this was the OPs question and you gave a good answer. — lexicore
– lexicore, Commented Apr 24, 2018 at 21:32

Ousmane D. · Accepted Answer · 2018-04-24 21:28:59Z

5

Using IntStream.range:

IntStream.range(1, checkers.size())
         .forEach(i -> checkers.get(i-1).setNextChecker(checkers.get(i)));

or using a for loop:

for (int i = 1; i < checkers.size(); i++) 
      checkers.get(i-1).setNextChecker(checkers.get(i));

edited Apr 24, 2018 at 21:28

answered Apr 24, 2018 at 17:50

Ousmane D.

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3 Comments

lexicore Over a year ago

Also one could write a for-loop without get(i).

Ousmane D. Over a year ago

@lexicore I am assuming you mean the for-each loop or also known as the enhanced for loop ?, if so wouldn't that make things a little bit less readable than the current for loop?

20 fps Over a year ago

Thanks, that's something I was looking for) I agree, that Stream API is not the best choice here, but I was not able to find that solution fast, so I asked this question here.

Andy Turner · Accepted Answer · 2018-04-24 21:58:26Z

1

A crazy alternative:

Iterator<Checker> currentIt = checkers.subList(0, checkers.size() - 1).iterator();
Iterator<Checker> nextIt = checkers.subList(1, checkers.size()).iterator();
while (currentIt.hasNext()) {
  currentIt.next().setNextChecker(nextIt.next());
}

I guess that you could also write it with a single iterator:

Iterator<Checker> it = checkers.iterator();
Checker previous = it.next();
while (it.hasNext()) {
  previous.setNextChecker(previous = it.next());
}

But assuming your list is small, and RandomAccess, I'd just stick with an index-based loop:

for (int i = 0; i < checker.size()-1; ++i) {
  checkers.get(i).setNextChecker(checkers.get(i+1));
}

Streams aren't really a benefit here.

answered Apr 24, 2018 at 21:58

Andy Turner

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2 Comments

Thiyagu Over a year ago

previous.setNextChecker(previous = it.next()); Seems crazy too :)

Andy Turner Over a year ago

@user7 yes, it's confusing enough that I had to try it to convince myself it would evaluate correctly.

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