Java Initialize ArrayList From For-Loop

Question

Is there a way to combine the two commands below into a single line, where I initialize the ArrayList using the for-loop?

ArrayList<KSE> kseList = new ArrayList<KSE>();
for (KSE k : allKSEs) if (k.isKeyPress()) kseList.add(k);

The variable allKSEs is just a generic Collection

Collection<KSE> allKSEs = KSE.parseSessionToKSE(ksListString);

If you initialize the ArrayList in your for loop, won't its contents be deleted or overwritten at each iteration of the loop? — Chamatake-san
– Chamatake-san, Commented Apr 29, 2015 at 23:01
Sometimes readability is worth one or two line more. (Personally I don't even like the one-line-for-if) — Enrichman
– Enrichman, Commented Apr 29, 2015 at 23:05

John Kugelman · Accepted Answer · 2015-04-29 23:02:19Z

3

In Java 8, you can use the new streaming syntax:

List<KSE> kseList = allKSEs.stream()
    .filter(KSE::isKeypress)
    .collect(Collectors.toList());

Pre-Java 8, what you have is what I would write, though I wouldn't condense the loop into a single line.

answered Apr 29, 2015 at 23:00

John Kugelman

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2 Comments

Unfortunately the project is written in Java 7. I don't have the ability to change that.

I know it's not proper style to condense the loop to one line. I was just trying to make it as compact as possible.

user1983983 · Accepted Answer · 2015-04-29 23:19:58Z

0

If you still use Java 7 you can use Apache CollectionUtils, Apache BeanUtils and the following code:

ArrayList<KSE> kseList = CollectionUtils.select(allKSEs, new BeanPropertyValueEqualsPredicate("keyPress", true));

answered Apr 29, 2015 at 23:19

user1983983

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