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

Two corrections:

1. You have to make an ArrayList of People objects:

   ArrayList preps = new ArrayList(); 
   

2. After adding the objects to the preps, use:

   Collections.sort(preps, new CompareId());
   

Also, add a CompareId class as:

class CompareId implements Comparator {  
    public int compare(Object obj1, Object obj2) {  
        People t1 = (People)obj1;  
        People t2 = (People)obj2;  

        if (t1.marks > t2.marks)  
            return 1;   
        else  
            return -1;
    }  
}