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Comparator and TreeSet

Henry Zhi Lin
Ranch Hand

Joined: Nov 04, 2008
Posts: 69
Hi, guys

The following code is Devaka's Exam Lab practice1 question 55.

WHy this have an runtime exception, I thought the treeset has a comparator to compare the value that saved into the set?

Can anyone explain to me how does this work?

SCJP 5.0
Ankit Garg

Joined: Aug 03, 2008
Posts: 9291

For inserting a class' element to a TreeSet, it must implement Comparable interface and override the compareTo method. This code is implementing Comparator interface and overriding compare method. Comparator is used when we want to use an external sorting logic which is different from the one in the class whose objects are being added to the TreeSet...

SCJP 6 | SCWCD 5 | Javaranch SCJP FAQ | SCWCD Links
I agree. Here's the link:
subject: Comparator and TreeSet
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