How to use Comparator in Java to sort

Question

I learned how to use the comparable but I\'m having difficulty with the Comparator. I am having a error in my code:

Exception in thread \"main\" java.lang.C         


        

Answer 1

You want to implement Comparable, not Comparator. You need to implement the compareTo method. You're close though. Comparator is a "3rd party" comparison routine. Comparable is that this object can be compared with another.

public int compareTo(Object obj1) {
  People that = (People)obj1;
  Integer p1 = this.getId();
  Integer p2 = that.getid();

  if (p1 > p2 ){
   return 1;
  }
  else if (p1 < p2){
   return -1;
  }
  else
   return 0;
 }

Note, you may want to check for nulls in here for getId..just in case.