Searched on Google with the first line of a JAVA stack trace?

We can recommend more relevant solutions and speed up debugging when you paste your entire stack trace with the exception message. Try a sample exception.

Recommended solutions based on your search

Solutions on the web

via Coderanch by Patrio Jensen, 1 year ago
SingletonCheck cannot be cast to java.lang.Comparable
java.lang.ClassCastException: SingletonCheck cannot be cast to java.lang.Comparable	at java.util.concurrent.ConcurrentSkipListMap.comparable(ConcurrentSkipListMap.java:621)	at java.util.concurrent.ConcurrentSkipListMap.doPut(ConcurrentSkipListMap.java:862)	at java.util.concurrent.ConcurrentSkipListMap.putIfAbsent(ConcurrentSkipListMap.java:1893)	at java.util.concurrent.ConcurrentSkipListSet.add(ConcurrentSkipListSet.java:202)	at test3.ThreadRunner.run(ThreadRunner.java:15)	at java.lang.Thread.run(Thread.java:619)