CODEWITHSUNDEEP
sortingcollectionsjava-8java-streamcomparator
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Reputation: 125

sort the list of objects for a record based on two dates(create date and update date)

In the below example I have a department with many cases. I need to get the latest case from the department where the sort order is based on udpatedTime (if udpatedTime is null have to consider createDate) and have to return the first item in the list that is the most recent one (either created or updated). For the newly created case, the updatetime would be null until a case is updated.

public class  Case{
    Long id;
    String number;
    String status;
    LocalDateTime createDate;
    String createdBy;
    LocalDateTime udpatedTime;
    String updatedBy;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public LocalDateTime getCreateDate() {
        return createDate;
    }

    public void setCreateDate(LocalDateTime createDate) {
        this.createDate = createDate;
    }

    public String getCreatedBy() {
        return createdBy;
    }

    public void setCreatedBy(String createdBy) {
        this.createdBy = createdBy;
    }

    public LocalDateTime getUdpatedTime() {
        return udpatedTime;
    }

    public void setUdpatedTime(LocalDateTime udpatedTime) {
        this.udpatedTime = udpatedTime;
    }

    public String getUpdatedBy() {
        return updatedBy;
    }

    public void setUpdatedBy(String updatedBy) {
        this.updatedBy = updatedBy;
    }
}





public class Department {
    String id;
    List<Case> allCases;

    Case latestCase;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public List<Case> getAllCases() {
        return allCases;
    }

    public void setAllCases(List<Case> allCases) {
        this.allCases = allCases;
    }

    public Case getLatestCase() {
        if (getAllCases().isEmpty()) {
            return null;
        }

        getAllCases().sort(new Comparator<Case>() {
            @Override
            public int compare(Case o1, Case o2) {
                if (o1.getUdpatedTime() != null) {
                    o1.getUdpatedTime().isAfter(o2.getUdpatedTime());
                } else if (o2.getUdpatedTime() != null) {
                    o1.getUdpatedTime().isAfter(o2.getUdpatedTime());
                }

                return 0;
            }
        });
return null;
    }
}

Upvotes: 2

Views: 124

Answers (1)

Misha
Misha

Reputation: 28143

You do not need to sort the list to get the most recent entry. Just use max:

import static java.util.Comparator.comparing;

getAllCases().stream()
     .max(comparing(
           c -> c.getUpdatedTime() == null ? c.getCreatedTime() : c.getUpdatedTime()
     ));

In java 9, you can replace the key extractor with c -> Objects.requireNonNullElse(c.getUpdatedTime(), c.getCreatedTime())

or c -> Objects.requireNonNullElseGet(c.getUpdatedTime(), c::getCreatedTime) (but that's probably overkill)

Upvotes: 3

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