sorting an arrayList<class> by its integer contents

Question

I am passing an arrayList to a method to sort its data. The data in the arrayList would contain multiple id numbers correlating to different students. the array will also include other information. How do i sort the arrayList by its id #. I believe it will have to do with my created class which is included below more code can be provided as necessary

public static class Student {

    public String firstName;    
    public String lastName;
    public Integer uid;     
    public StudentType type;

    public Student(Student orig) {
        this.firstName = orig.firstName;
        this.lastName = orig.lastName;
        this.uid = orig.uid;
        this.type = orig.type;
    }

    // construct a new student with given fields
    public Student(String firstName, String lastName, Integer newUid, StudentType type) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.uid = newUid;
        this.type = type;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getLastName() {
        return lastName;
    }
    //set type

    public void setType(StudentType type) {
        this.type = type;
    }
    //return type

    public StudentType getType() {
        return type;
    }
    public void setUid(Integer uid){
        this.uid = uid;
    }
     public Integer getUid() {
        return uid;
    }

    // return a string representation of the invoking object
    public String toString() {
        return firstName + " " + lastName + " " + uid + " " + type;
    }

    public static class Graduate extends Student {

        public boolean thesis;
        public ClassStanding study;
        public String profName;

        public Graduate(Student orig, boolean isThesis, ClassStanding study, String profName) {
            super(orig);
            thesis = isThesis;
            this.study = study;
            this.profName = profName;
        }

        public boolean getThesis() {
            return thesis;
        }

        public void setThesis(Boolean thesis) {
            this.thesis = thesis;
        }

        public ClassStanding getStudy() {
            return study;
        }

        public void setStudy(ClassStanding study) {
            this.study = study;
        }

        public String getProfName() {
            return profName;
        }

        public void setProfName(String profName) {
            this.profName = profName;
        }

        public String toString() {
            return super.toString() + thesis + " " + study + " " + profName;
        }
    }

    public static class UnderGraduate extends Student {

        public Major major;
        public Double overallGpa;
        public Double majorGpa;
        public ClassStanding study;

        public UnderGraduate(Student orig, Major major, Double overallGpa, Double majorGpa, ClassStanding study) {
            super(orig);
            this.study = study;
            this.major = major;
            this.overallGpa = overallGpa;
            this.majorGpa = majorGpa;
        }

        public void setMajor(Major major) {
            this.major = major;
        }
        //return type

        public Major getmMajor() {
            return major;
        }

        public void setOverallGPA(Double overallGpa) {
            this.overallGpa = overallGpa;
        }

        public Double getOverallGPA() {
            return overallGpa;
        }

        public void setMajorGPA(Double majorGpa) {
            this.majorGpa = majorGpa;
        }

        public Double getMajorGPA() {
            return majorGpa;
        }

        public ClassStanding getStudy() {
            return study;
        }

        public void setStudy(ClassStanding study) {
            this.study = study;
        }

        public String toString() {
            return study + " " + major + " " + overallGpa + " " + majorGpa;
        }
    }
}

Steve P. · Accepted Answer · 2013-11-18 23:05:16Z

1

Collections.sort(myListofStudents, new Comparator<Student>() {
    @Override
    public int compareTo(Student s1, Student s2) {
          return s1.getUid().compareTo(s2.getUid());
    }
});

Alternatively, you can have Student implement Comparable<Student>, which means including a .compareTo().

NB: If you're going to override .compareTo(), you should override .equals(), which means you should override hashCode().

answered Nov 18, 2013 at 23:05

Steve P.

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Comments

Dani · Accepted Answer · 2013-11-18 23:04:39Z

0

Define a Comparator<Student> and use it with Collections.sort:

public class StudentComparator implements Comparator<Student> {
    @Override
    public int compare (Student s1, Student s2) {
        // Your comparison logic here
    }
}

...then...

Collections.sort(data, new StudentComparator());

See the JavaDoc on Comparator for more information.

answered Nov 18, 2013 at 23:04

Dani

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vangelion · Accepted Answer · 2013-11-18 23:06:36Z

0

Create a Comparator for Student, then use Collections.sort()

answered Nov 18, 2013 at 23:06

vangelion

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