Collections.sort with multiple fields

Question

I have a list of "Report" objects with three fields (All String type)-

ReportKey StudentNumber School 

I have a sort code goes like-

Collections.sort(reportList, new Comparator<Report>() {  @Override public int compare(final Report record1, final Report record2) {       return (record1.getReportKey() + record1.getStudentNumber() + record1.getSchool())                               .compareTo(record2.getReportKey() + record2.getStudentNumber() + record2.getSchool());       }  }); 

For some reason, I don't have the sorted order. One advised to put spaces in between fields, but why?

Do you see anything wrong with the code?

Answer 1

Do you see anything wrong with the code?

Yes. Why are you adding the three fields together before you compare them?

I would probably do something like this: (assuming the fields are in the order you wish to sort them in)

@Override public int compare(final Report record1, final Report record2) {     int c;     c = record1.getReportKey().compareTo(record2.getReportKey());     if (c == 0)        c = record1.getStudentNumber().compareTo(record2.getStudentNumber());     if (c == 0)        c = record1.getSchool().compareTo(record2.getSchool());     return c; }