why to implements Comparator not simply Comparator

Question

class problemsolver implements Comparator<Student> {

   public int compare(Student obj1,Student obj2) {
       return obj1.fname.compareTo(obj2.fname);
   } 
}

When I write simply class problemsolver implements Comparator it is showing this error.

prog.java:25: error: problemsolver is not abstract and does not override abstract method compare(Object,Object) in Comparator

Why?

Because Comparator has a generic type parameter, and leaving that out is wrong. Learn about generics, in while doing so, you also learn why to not leave them out. — GhostCat, Jun 13 '18 at 08:50

score 2 · Accepted Answer · answered Jun 13 '18 at 08:44

2

Implicitely Comparator is Comparator<Object>, then compiler expects you to implements compare(Object, Object).

What you need is :

class problemsolver implements Comparator<Student>

answered Jun 13 '18 at 08:44

yunandtidus

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why to implements Comparator not simply Comparator

1 Answers1