Using the Same Stream flow for else condition in Java8

Question

On the way of refactoring the below code snippet to java8 using streams

private Date getDate(List<BrowseHistory> historyList, String subscribe, String cancelled) {
    for(int i=0; i<= historyList.size(); i++) {
        if(isContainsStatus(historyList.get(i), subscribe) && isExist(historyList, cancelled, i)) {
            return historyList.get(i).getCreated()
        }
    }
    return null;
}

private boolean isExist(List<BrowseHistory> historyList, String status, int i) {
        return historyList.size() == i+1 || (isContainsStatus(historyList.get(i+1), status) || isContainsStatus(historyList.get(i+1), Status.PEND.toString()));
    }

private boolean isContainsStatus(BrowseHistory history, String status) {
        return history.getStatus().contains(status);
    }

I could able to refactor till the if block, with java8 filter.

Below is the Java8 refactored code

private Date getDate(List<BrowseHistory> historyList, String subscribe, String cancelled) {
return IntStream.range(0, historyList.size())
        .filter(i -> isContainsStatus(historyList.get(i), subscribe) && isStatusExist(historyList, cancelled, i))
        .mapToObj(historyList::get)
        .map(BrowseHistory::getCreated)
        .findFirst() // find first that got through those filters
        .orElse(null);

}

Edited the java8 refactored code based on the below answer.

You're returning exactly the same in both branches of the if. Besides, I think you have a problem with the index as it will be out of bounds in the last iteration (or maybe in the previous one). Why are you iterating by the index instead of directly over the elements of the list? — fps
– fps, Commented Feb 4, 2018 at 3:45
I dont think it will throw index out of bound because of the inner if, and coming to the index iteration I always wants to check the next element in the list if I'm in the current element. Is there any way to do this with iterating over the elements? — Digital
– Digital, Commented Feb 4, 2018 at 13:46

KKaar · Accepted Answer · 2018-02-04 23:37:33Z

4

There should be identical method in java 8 to the one that you had there pre-java-8.

private Date getDate(List<BrowseHistory> historyList, String subscribe, String cancelled) {
    return IntStream.range(0, historyList.size())
            .filter(i -> isContainsStatus(historyList.get(i), subscribe) && isStatusExist(historyList, cancelled, i))
            .mapToObj(historyList::get)
            .map(BrowseHistory::getCreated)
            .findFirst() // find first that got through those filters
            .orElse(null);
}

Few notes though:

In for loop conditional i <= historyList.size() I would rather use i < historyList.size()
The Java-8 solution identical to your method isn't too good looking, there might be another solutions, but this would be one.

edited Feb 4, 2018 at 23:37

answered Feb 4, 2018 at 17:37

KKaar

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2 Comments

Digital Over a year ago

Thanks KKaar, your suggestion is much helpful. edited the posted question based on the suggestion provided by you

KKaar Over a year ago

No problem @Digital, if there is still something that's bothering related to this question just let know. Kind of everything is doable with Java-8. Some solutions just are not so good looking so the actual solution in J8 might not be the best one to read to. Edited answer to relate the question.

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