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Treeset Cannot Be Cast To Comparable

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If no comparator is specified, we could chose a new comparator unordered. super T, Tuple2http://bovbjerg.net/cannot-be/treemap-cannot-be-cast-to-comparable.php

The implementations of Traversable are overloaded there, relying on the RedBlackTree backend, which needs a comparator. This is spelled out in the documentation for SortedSet: All elements inserted into a sorted set must implement the Comparable interface (or be accepted by the specified comparator). How do I make an alien technology feel alien? That's right.

Cannot Be Cast To Java.lang.comparable Treemap

If the class doesn't have a natural ordering, or if you don't want to use the natural ordering in this particular case, then that's when you need a Comparator. Instead we can compare the hashCodes (with null values ordered first) as fallback. SCJP 1.4 - SCJP 6 - SCWCD 5 - OCEEJBD 6 - OCEJPAD 6 How To Ask Questions How To Answer Questions Laythe Chamse Greenhorn Posts: 15 posted 7 years If the API docs makes it clear how it works, with an additional example (downcasting to a Set and calling flatMap), this sounds like a reasonable solution.

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  • There's no way around it. –user2357112 Feb 6 '14 at 2:08 add a comment| 2 Answers 2 active oldest votes up vote 2 down vote accepted You'll notice the javadoc of
  • But this is not possible in the case of empty collections where we can't take an element to check if it is comparable.
  • Even if there are situations that do not work (as Ruslan has shown), i favor to implement it similar to Benoits suggestion.

Related 0Error: “Exception in thread ”main“ java.lang.ClassCastException: manycard.Main$Card cannot be cast to java.lang.Comparable”3'java.lang.ClassCastException: Resource cannot be cast to java.lang.Comparable'-2ClassCastException when casting an Object to List0java.lang.ClassCastException, DeepNodeListImpl cannot be cast3MyClass cannot be Rob Spoor Sheriff Posts: 20720 68 I like... Can you dispel a magic effect you can't perceive? Java Implement Comparable How to reduce the width of the equation in a text paragraph?

The code for creating the TreeSet with a Comparator is dead simple - there's a constructor that takes a Comparator as an argument: TreeSet tree = new TreeSet(comparator); To create the Treeset Comparable Example Join them; it only takes a minute: Sign up List to TreeSet conversion produces: “java.lang.ClassCastException: MyClass cannot be cast to java.lang.Comparable” up vote 11 down vote favorite 2 List myclassList = In order to be able to determine that order, the entries must implement the Comparable interface so that that order can be determined. click take(0) and then perend(elem) etc.).

You need to create a class that implements this interface and provide an instance of it to your TreeMap constructor expression. Arraylist Is Ordered While Hashset Is Not extends T1, ? Laythe Chamse Greenhorn Posts: 15 posted 7 years ago David Newton wrote:Depends--how do you want MyOwnClass to be compared to other instances? Rob Spoor Sheriff Posts: 20720 68 I like...

Treeset Comparable Example

Actually, the latter would have given a compiler error since Java 5.0, but before it would have given the error. https://coderanch.com/t/461391/java/TreeSet-RuntimeException-code and what about if i wanted MyOwnClass to be compared to String and Integer at the same time is that possible? Cannot Be Cast To Java.lang.comparable Treemap How to move VIM file to outside of the terminal? Cannot Be Cast To Java.lang.comparable Java extends V> m) { return new TreeMap(m); } public static create(SortedMap

TreeSet.empty() et al, could still use the naturalComparator. this contact form Ravi Kiran Va Ranch Hand Posts: 2234 I like... But why this is required only for TreeSet class ?? Your code needs minor changes. Treeset Comparator Example

The underlying RedBlackTree performs a binary search along the left/right tree branches. If no comparator is specified we take the naturalComparator for elements of type U (even if elements of U are not comparable - that's also the way java.util.SortedSet is working). TreeSets are sorted sets and require either objects to be Comparable or a Comparator to be passed in to determine how to sort the objects in the Set. have a peek here Personal Open source Business Explore Sign up Sign in Pricing Blog Support Search GitHub This repository Watch 75 Star 1,285 Fork 153 javaslang/javaslang Code Issues 87 Pull requests 9 Projects

It is no viable solution to search (once) for the most common comparator of two objects o1, o2. Comparable Interface Java Then the resulting SortedSet would be equivalent to an unordered Set. more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed

Update: Of course this does not make any sense at all (using -1 instead of hash(o1, o2)) because binary search within the tree isn't possible any more.

java tutorial : Blog to learn java programming Home Java Elasticsearch Hadoop Databases Caching XML R Tutorial for beginners Python Julia Haskell Documentation Saturday, 19 April 2014 TreeSet : add : asked 2 years ago viewed 3793 times active 1 year ago Upcoming Events 2016 Community Moderator Election ends Nov 22 Linked 1 Why Map interface does not restrict key generic type posted 6 years ago Edit: reply to Ravi's question why it was only required for TreeSet It isn't. Java Treeset Example import java.util.TreeSet; class Dog { int size; Dog(int s) { size = s; } } public class ImpComparableWrong { public static void main(String[] args) { TreeSet i =

I just want to use a Set to filter the unique elements of the List since my List contains unncessary duplicates. Implement methods for Iterator using Generics for TreeSet Quick Question All times are in JavaRanch time: GMT-6 in summer, GMT-7 in winter Contact Us | advertise | mobile view | Powered What am I doing wrong here? 2 Why am I getting a class cast exception if I have implemented comparator? Check This Out JΛVΛSLΛNG member danieldietrich commented Mar 24, 2016 In Java we can provoke the same, but it is not so easy to do the wrong thing as with Javaslang because we have

US Election results 2016: What went wrong with prediction models? This would be a breaking change :-/ The other idea was to keep the API and internally use an `unordered comparator' instead (if that is possible). more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed Actualy i am studing the java colection, i am done with the HashSet and i had a homework just like this one in HashSet as well and i have done it,

The Java tutorials have a section giving more detail on all this at http://download.oracle.com/javase/tutorial/collections/interfaces/order.html. super U, ? when calling min() and max(). JΛVΛSLΛNG member danieldietrich commented Oct 7, 2016 Just returning -1 seems like the only plausible way to resolve the hash collision, but that itself smells as well.

How would I call that in this code? –Mxt Feb 6 '14 at 2:11 @Mxt Comparator is an interface. It is important to provide a safe API, i.e. US Election results 2016: What went wrong with prediction models? On the scala side, their SortedSet.flatMap returns either a Set or TreeSet depending on what you map to.

Jaydeep Vaishnav Greenhorn Posts: 16 posted 7 years ago Use the following code. o1.hashCode() != o2.hashCode() for two different objects o1, o2. Henry Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor) Matthew Brown Bartender Posts: 4568 9 posted 5 years ago And if you don't want them Remember, TreeMap implements SortedSet, so it has to know how to order the elements one way or another.

Thanks for the great work guys, and keep going ;) Cheers, /Benoit 👍 1 JΛVΛSLΛNG member danieldietrich commented Mar 24, 2016 Hi @benoitheinrich, the existing comparator is related to elements