java.lang.IncompatibleClassChangeError, BM25BooleanQuery

Question

Exception in thread "main" java.lang.IncompatibleClassChangeError: Implementing class
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    at NVoting.<init>(NVoting.java:143)
    at Main.main(Main.java:8)

on this line:

booleanQuery.add(new BM25BooleanQuery(current_tags[i], 
                            "tags",
                            new StandardAnalyzer(org.apache.lucene.util.Version.LUCENE_31)), 
                            BooleanClause.Occur.SHOULD);

I'm using an implementation of BM25 Okapi retrieval system: http://nlp.uned.es/~jperezi/Lucene-BM25

Can you help me to fix the issue ? I'm using Lucene 3.1 I've also tried Lucene 2.9.4 with no luck.

thanks

This may be helpful http://stackoverflow.com/questions/1980452/what-causes-java-lang-incompatibleclasschangeerror It means you are trying to use two libraries which were not compiled together and have a breaking change between them i.e. they are incompatible. — Peter Lawrey, Apr 19 '11 at 12:56

score 1 · Answer 1 · answered Apr 19 '11 at 12:56

Either you use different third-party libraries for compilation and execution or some of your third-party libraries are not compatible.

The error may happen if you use one version of a library for compilation and another one (with slightly different API) for execution. Double check all your library versions (do they fit?) and you classpaths.

score 0 · Accepted Answer · answered Apr 19 '11 at 13:00

I'm not a Java programmer, so take this answer with caution, but here's the facts as I see them:

The last update date of the BM25 implementation is January 2009 (or perhaps December 2009)
Lucene 3.1 was released in March this year
IncompatibleClassChangeError indicates an incompatible change in a dependent class

So I think you'll either need to use the same version of Lucene as the BM25 implementation used when it was built or rebuild it from source (if that's a possibility).

Good luck,

java.lang.IncompatibleClassChangeError, BM25BooleanQuery

2 Answers2