CLASSCASTEXCEPTION CANNOT BE CAST TO COMPARABLE

You can’t expect to wield supreme executive power just because. PDF with Java https: Your class has not implemented Comparable interface. Other option is to pass a Comparator Object to TreeMap http: Map Keys need to be comparable to ensure a sort order in the map. To do that it either needs a Comparator or if you don’t provide one the element-class must implement the Comparable interface. Good programmers write code that humans can understand. Till today i was adding Strings so didn’t realized that , but when i added Custom Object the concept was clear.

If you’re still confused read this. How do I get MyVertex types to be casted to Comparables? MyVertex cannot be cast to java. I am getting the following error from Java:. You would have had the same error when using these objects in a TreeMap, or when they were in a List and you sorted it using Collections. I am getting the following error from Java: That would still be a possible type safety problem waiting to happen. This question has been asked before and already has an answer.

Stack Overflow works best with JavaScript enabled. How do I get MyVertex types to be casted to Comparables? That allows me to technically create a SortedSet implementing class which uses the system hash code for ordering. I ckasscastexception using the Java JungI graph package and Netbeans 7. MyVertex cannot be cast to java. Why is this necessary?

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TreeSet and TreeMap use sorting for their internal storage. A question About overriding equals and hashcode for an Object. That would still be a possible type safety problem waiting to happen.

Map Keys need to be comparable to ensure a sort order in the map.

Java – Compare Object (Comparable) (Collection Sort)

Cznnot would not require a comparator so comparator returns null but the elements are still not Comparable. To do that it either needs a Comparator or if you don’t provide one the element-class must implement the Comparable interface. Question 10 Chapter 7: MyVertex class should implement Comparable as tree map uses the compareTo method to order the map based on keys.

Thanks Wouter, it was nice explanation.

casting – Java “cannot cast to Comparable” when using TreeMap – Stack Overflow

Employee cannot be cast to java. You should also take care that you parameterize your generic types correctly.

Other option is to pass a Comparator Object to TreeMap http: The behaviour is compliant with the javadoc of TreeMap:. Some structures or methods simply require Comparables. Actually, the latter would have given a compiler error since Java 5. This question has been asked before and already has an answer. I am comparabld the following error from Java:. I do not immediately see the reason. Overloading and NOT overriding equals method.

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PDF with Java https: Till today i was adding Strings so didn’t realized thatbut when i added Custom Object the concept was clear. BystrupMatten Jan 3 ’13 at Because you are storing in tree map which is a sorted map sorted by keys.

cannot be cast to java.lang.Comparable

The TreeSet orders it’s elements. If you’re still confused read this. If those answers do not fully address your question, please ask a new question.

Your Employee class needs to implement the Comparable interface or you need to provide a Comparator to the TreeSet. Note clssscastexception before Java 7, the exception would only be thrown when adding a second item to the map whereas with Java 7 the exception is thrown when adding one item to the map.

You have method compareTo ; so just add implements Comparable to your class MyVertex. I am getting the following error from Java: Comprable ClassCastException if the specified key cannot be compared with the keys currently in the map There are essentially two ways to make it work: Removing any of the constructors was not an option as it would break older code.

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