CODEWITHSUNDEEP
javalistjava-8
Renaud is Not Bill Gates
Renaud is Not Bill Gates

Reputation: 2074

Best way to modify objects in list using values from another list

I have an entity Issue as following :

public class Issue{
    private IssueElementEnum issueElement;
    private IssueTypeEnum issueType;
    private String title;
}

And I have a list of Issue which I get from DAO:

List<Issue> issues = issueDAO.findAll();

In this list I have some Issue object where issue.getIssueElement() == IssueElementEnum.USER, I want to update these object by changing there title field, for that I have to filter the list of issues and create a list of type String from the result list, then I have to pass this list to a service that will return a list of new titles which will be used to replace the old titles.

This is what I tried :

List<Issue> issues = issueDAO.findAll();
List<Issue> userIssues = issues.stream().filter(a -> a.getIssueElement() == IssueElementEnum.USER).collect(Collectors.toList());
List<String> oldTitles = userIssues.stream().map(a -> a.getTitle()).collect(Collectors.toList());
List<User> users = userSVC.findByTitles(oldTitles);
for (User user : users) {
    for (Issue issue : issues) {
        if (user.getKey().equals(issue.getTitle())) {
            issue.setTitle(user.getFirstName() + " " + user.getLastName());
        }
    }
}

Is there any other way to write this ?

Upvotes: 0

Views: 58

Answers (1)

Paul Boddington
Paul Boddington

Reputation: 37645

It's quite hard to follow exactly what's going on here, but there are 2 improvements I can spot.

Firstly, there is no point in userIssues at all (although it seems odd that in the last step you iterate over all issues rather than userIssues. Is this right?). Just do

List<String> oldTitles = issues
                            .stream()
                            .filter(a -> a.getIssueElement() == IssueElementEnum.USER)
                            .map(Issue::getTitle)
                            .collect(Collectors.toList());

Secondly, the nested loops appear unnecessary. I'm not 100% clear on your logic but something like this ought to work.

Map<String, User> usersByKey = new HashMap<>();
for (User user : users)
    usersByKey.put(user.getKey(), user);
for (Issue issue : issues) {
    User user = usersByKey.get(issue.getTitle());
    if (user != null) 
        issue.setTitle(user.getFirstName() + " " + user.getLastName());
}

Upvotes: 1

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