How to get specific object from list of objects by using unique id of that object in java?

Question

I want specific object with all it's values by using it's unique id of object from object list.

I have tried but i am getting index -1 while running below code.

List<JobDataDetail> jobList = getJobList();
JobDataDetail object = jobList.get(jobList.indexOf(new JobDataDetail(jobReferenceId)));

from the class

public class JobDataDetail implements Serializable,Comparable<JobDataDetail> {

    public int jobSequence;
    public String jobReferenceId;
    public String jobAddress;
    public String jobScheduledDate;

    public JobDataDetail() {
        super();
        // TODO Auto-generated constructor stub
    }

    public JobDataDetail(int jobSequence){
        super();
        this.jobSequence = jobSequence ;
    }
    public JobDataDetail(String jobReferenceId){
        super();
        this.jobReferenceId = jobReferenceId;
    }

    public int getJobSequence() {
        return jobSequence;
    }
    public void setJobSequence(int jobSequence) {
        this.jobSequence = jobSequence;
    }
    public String getJobReferenceId() {
        return jobReferenceId;
    }
    public void setJobReferenceId(String jobReferenceId) {
        this.jobReferenceId = jobReferenceId;
    }
    public String getJobAddress() {
        return jobAddress;
    }
    public void setJobAddress(String jobAddress) {
        this.jobAddress = jobAddress;
    }
    public String getJobScheduledDate() {
        return jobScheduledDate;
    }
    public void setJobScheduledDate(String jobScheduledDate) {
        this.jobScheduledDate = jobScheduledDate;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result
                + ((jobReferenceId == null) ? 0 : jobReferenceId.hashCode());
        result = prime * result + jobSequence;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        JobDataDetail other = (JobDataDetail) obj;
        if (jobReferenceId == null) {
            if (other.jobReferenceId != null)
                return false;
        } else if (!jobReferenceId.equals(other.jobReferenceId))
            return false;
        if (jobSequence != other.jobSequence)
            return false;
        return true;
    }

    @Override
    public int compareTo(JobDataDetail another) {
        return this.getJobReferenceId().compareTo(another.getJobReferenceId());
    }

}

Answer 1

我已经从equals方法中删除了jobSequence条件检查，它正在工作。

Answer 2

List.indexOf() uses equals() method to compare objects.

In your case, you are assuming that two objects with same jobReferenceId are equals but your equals() method doesn't say so ( because of the jobSequence test at the end of your method ).

---

If you want to get an item from your list by one of its attribute, the easiest way would be using filter expression in Java 8:

JobDataDetail job = jobList.stream()
                           .filter(j -> j.getAttribute().equals(someValue))
                           .findFirst();

If Java 8 is not an option, I would go for a classic for loop iterating over the list.