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Java.lang.classcastexception Cannot Be Cast To Java.lang.comparable Treemap


Lastly, I don't think it's been said here, but this same issue probably applies to .map as well. This will first operate on a Comparator that 1. new TreeMap(new Comparator() { public int compare(MyVertex o1, MyVertex o2) { //comparison logic goes here } }); Why is this necessary? I am using the Java JungI graph package and Netbeans 7. click site

What do I do? Already have an account? With Comparable Not possible, you can sort the objects in the (only) way defined in compareTo() method. We are mapping to elements of type U, therefore we need a new comparator. http://stackoverflow.com/questions/14133600/java-cannot-cast-to-comparable-when-using-treemap

Cannot Be Cast To Java.lang.comparable Treeset

Should you change a thermostat when changing your water pump What crime would be illegal to uncover in medieval Europe? Ravi Kiran Va Ranch Hand Posts: 2234 I like... If you want to sort using different order then you need to provide your own comparator. posted 6 years ago Edit: reply to Ravi's question why it was only required for TreeSet It isn't.

Christophe Verré Sheriff Posts: 14691 16 I like... However, it is still unsafe. We should return -1 instead. Cannot Be Cast To Java.lang.comparable Priority Queue You need to create a class that implements this interface and provide an instance of it to your TreeMap constructor expression.

naturalComparator.compare(o1, o2) : unorderedComparator.compare(o1, o2); } private boolean useNatural(final T o1, final T o2) { if (useNatural == null) { useNatural = o1 instanceof Comparable || o2 instanceof Comparable; } return Nevertheless, having a fallback that just works would be great. I agree that it is a tough decision to break the API by returning a Set instead of a SortedSet. Do a search around, that question has been asked before.

posted 7 years ago You can compare on two fields; first on one, and if that would lead to equality the other as well. Java Treemap Comparator Example this is the Error i get: Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer Can i make TreeSetX to hold a String and Integer at the same time? Thanks in advnace . Good programmers write code that humans can understand." --- Martin Fowler Please correct my English.

Cannot Be Cast To Java.lang.comparable Java

Rob Spoor Sheriff Posts: 20720 68 I like... navigate to these guys If you want to sort a TreeSet of Strings in descending order there is an example here - http://netjs.blogspot.com/2015/10/how-to-sort-elements-in-different-order-tree-set-java.html asdf asdfg Mohammed Very Useful… Ruchika Thanks.. Cannot Be Cast To Java.lang.comparable Treeset Thanks for the kind words :-) Daniel benoitheinrich commented Mar 24, 2016 Hi @danieldietrich, Thanks for the quick answer !! Treeset Comparable Example Good programmers write code that humans can understand." --- Martin Fowler Please correct my English.

What do the keys and values represent? http://tcsmacs.net/cannot-be/java-lang-classcastexception-ljava-lang-object-cannot-be-cast-to-pojo.php super E>> create(Collection

The underlying RedBlackTree performs a binary search along the left/right tree branches. For instance, don't use:Set set = new TreeSet()Use this instead:Set set = new TreeSet()This has nothing to do with your problem, but it's good practice to get used to. Imagine the TreeSet.contains(value) method. navigate to this website I think the hash(o1, o2) method is a good solution as fallback for non-equal objects. (see also notes below) final class ObjectComparator implements java.util.Comparator, Serializable { private static final long serialVersionUID

was looking for the same thing Archives August 2016(4) April 2016(1) December 2015(2) September 2015(1) August 2015(1) July 2015(2) June 2015(1) May 2015(3) April 2015(5) March 2015(9) February 2015(2) January 2015(8) Treeset Comparator Is adding the ‘tbl’ prefix to table names really a problem? public class ComparatorTest { @org.junit.Test public void compare() throws Exception { java.util.Comparator wonkyComparator = new Comparator(); // ints assertEquals(Integer.compare(5, 9), wonkyComparator.compare(5, 9)); // anon objects Object a = new Object(){ int

java exception collections set treeset share|improve this question asked Apr 11 '13 at 7:31 Rais Alam 4,458104381 Employee must implement the interface Comparable to be able to use Treeset.

But this is not possible in the case of empty collections where we can't take an element to check if it is comparable. super T, ? We can't check the special case where T is U. Java Implement Comparable Your inner class must have static qualifier: otherwise it can not be constructed without implicit "this" argument.

Rob Spoor Sheriff Posts: 20720 68 I like... Your class does not. This would allow proper deserialization. my review here Checking for hashCode collisions would be problematic.

How much time would it take for a planet scale Miller-Urey experiment to generate intelligent life Someone peeled an American flag sticker off of my truck. import java.util.TreeSet; class Dog { int size; Dog(int s) { size = s; } } public class ImpComparableWrong { public static void main(String[] args) { TreeSet i = Reload to refresh your session.