Object and Comparable

[naveen yadav]

Hi, ranchers

Object class does not implements the Comparable<E> interface then why following code do not throw ClassCastEXception?

import java.util.*;
class Testu{
public static void main(String[] args) 
{

TreeSet ts = new TreeSet();
ts.add(new Object());

}
}

[Harsha Smith]

It does throw Class cast exception when more than one object is added to the set.

[naveen yadav]

Why so?

[Harsha Smith]

only when size is greater than 1 comparision is done between elements. see how it works in treeset class thats present in src.zip in your jdk folder.

[Matthew Brown]

Sort algorithms work by comparing pairs of objects - you need two objects to be able to call compareTo. Until you have a pair of objects, it can't be called.