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Treemap Cannot Be Cast To Comparable


share|improve this answer answered Jan 3 '13 at 5:38 assylias 178k26340491 last note is interesting –Subin Jan 3 '13 at 5:46 add a comment| up vote 5 down vote Thanks in advnace . Lastly, I don't think it's been said here, but this same issue probably applies to .map as well. import java.util.TreeSet; class Dog { int size; Dog(int s) { size = s; } } public class ImpComparableWrong { public static void main(String[] args) { TreeSet i = have a peek here

Is adding the ‘tbl’ prefix to table names really a problem? I know a HashMap would eliminate this problem, but I have to use a TreeMap. –Mxt Feb 6 '14 at 2:05 Well, if you need a TreeMap (dunno why The first non-null element of a set may be a Comparable, but a) that doesn't guarantee that the other non-null elements of the set are Comparable and b) doesn't guarantee that posted 6 years ago Some structures or methods simply require Comparables. http://stackoverflow.com/questions/14133600/java-cannot-cast-to-comparable-when-using-treemap

Cannot Be Cast To Java.lang.comparable Treeset

nasty. 👍 1 JΛVΛSLΛNG member danieldietrich commented Sep 29, 2016 The breaking change is a tough pill. If you're worried about performance then you could maybe remove the method call and put everything in the compare() method. Build me a brick wall!

Vijitha Kumara Bartender Posts: 3919 10 I like... current community chat Stack Overflow Meta Stack Overflow your communities Sign up or log in to customize your list. posted 6 years ago Till today i was adding Strings so didn't realized that , but when i added Custom Object the concept was clear . Cannot Be Cast To Java.lang.comparable Priority Queue 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).

How does Gandalf end up on the roof of Isengard? Cannot Be Cast To Java.lang.comparable Java That's right. final class ObjectComparator implements java.util.Comparator, Serializable { private static final long serialVersionUID = 1L; private static final ObjectComparator INSTANCE = new ObjectComparator<>(); private ObjectComparator() { } @SuppressWarnings("unchecked") static ObjectComparator instance() The simplest solution seems to be the best: breaking backward-compatibility :-/ Update/Note: I think also a cycle detection is needed in the solution below (for mutable objects that contain a self-reference

super K> comparator) { return new TreeMap(comparator); } public static { int size; Dog(int s) { like this: O------------------------ / \ T extends Comparable T' / \ / \ T1 T2 T3 T4 Example: Set set = Set.of(t1, t2, t3, t4); where t1 of type T1, t2

Cannot Be Cast To Java.lang.comparable Java

Possible repercussions from assault between coworkers outside the office When does TNG take place in relation to DS9? JΛVΛSLΛNG member danieldietrich commented Sep 19, 2016 Hi @kag0, thanks for your thoughts. Cannot Be Cast To Java.lang.comparable Treeset And this is the homework: * Create your own NetBeans project named as MyTreeSet * Create your own TreeSet object * Add the following objects to the newly created MyTreeSet object Treeset Comparable Example Even if there are situations that do not work (as Ruslan has shown), i favor to implement it similar to Benoits suggestion.

For example:

 String foo = "bar"; 
Yishagerew lulie There are actually various ways to implement a comparator inside a class without implementing the comparator interface, here is one.
Sorted sets are described by the SortedSet interface. super Integer, ? The same thing applies for Map methods... Treemap Comparable Example

  1. take(0) and then perend(elem) etc.).
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  3. Join them; it only takes a minute: Sign up What causes the ClassCastException: java.util.TreeSet cannot be cast to java.lang.Comparable?
  4. and what about if i wanted MyOwnClass to be compared to String and Integer at the same time is that possible?
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This will first operate on a Comparator that 1. Your compareTo implementation should describe how a Fegan compare to another Fegan. more hot questions question feed lang-java about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Check This Out posted 6 years ago Your Employee class needs to implement the Comparable interface or you need to provide a Comparator to the TreeSet. "Any fool can write code that a computer

Terms Privacy Security Status Help You can't perform that action at this time. Treeset Comparator Laythe Chamse Greenhorn Posts: 15 posted 7 years ago Jaydeep Vaishnav wrote:It seems that you are supposed to work with HashSet and not TreeSet. Given the hints solve the puzzle How can I save a file to a new location from inside Vim?

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JΛVΛSLΛNG member danieldietrich commented Mar 24, 2016 Thank you @benoitheinrich, you are right. posted 7 years ago A TreeSet isn't meant to hold different kinds of objects, because all these objects need to be compared to each other. up vote 0 down vote favorite So I'm trying to move all Strings of a certain length from a Collection of Strings (could either be a Set or a List) to Java Implement Comparable Furniture name for waist-high floor-sitting shelf cabinet thing Is it possible to check where an alias was defined?

Why is the 'You talking to me' speech from the movie 'Taxi Driver' so famous? Even better would be to take the naturalComparator, if there exsists an order and the unordered comparator as fallback. posted 6 years ago Edit: reply to Ravi's question why it was only required for TreeSet It isn't. http://bovbjerg.net/cannot-be/treemap-cannot-be-resolved-to-a-type.php Given the definition of your class, how would TreeSet know how to sort instances of it?

I think the the RedBlackTree should still work. Take a look at TreeMap.put(K key, V value) source codes and you'll clearly see the reasons behind all your questions (TreeSet is based on TreeMap, hence the source reference). 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). HashSet vs.

I agree that it is a tough decision to break the API by returning a Set instead of a SortedSet. 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 Do you think this could work? If you don't fulfil these requirements, the sorted set won't know how to compare its elements and won't be able to function.

super E> comparator) { return new TreeSet(comparator); } public static

Do the Leaves of Lórien brooches have any special significance or attributes? Thanks Wouter, it was nice explanation . With Comparable Not possible, you can sort the objects in the (only) way defined in compareTo() method. Is it possible to hand start modern planes?

We should move null values out of the way (nulls-first strategy).