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class cast exception

 
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Posts: 38
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plz explain the reason for class cast exception....
import java.util.*;
public class Test1{
public static void main(String a[]){
Set s = new TreeSet();
s.add(new Person(20));
s.add(new Person(10));
System.out.println(s);
}
}
class Person{
Person(int i){}
}
 
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All elements inserted into the set must implement the Comparable interface.
 
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