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Exception in adding values in treeset

 
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Hi,
I am trying to add few few objects to treeset, but it is giving me an exception "Exception in thread "main" java.lang.ClassCastException: demo.People cannot be cast to java.lang.Comparable"
Any idea on this? Below is the code snippet that I am trying.




 
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With a TreeSet, elements either have to be Comparable, or otherwise, you must provide a Comparator that can compare the elements. Without either, the TreeSet will not be able to sort the elements.

As for the error that you are seeing, you didn't provide a Comparator, so the TreeSet assumes that it is Comparable -- and throws an exception when the cast is attempted.

Henry
 
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