Running a console based verifier java org.apache.bcel.verifier.Verifier fully.qualified.class.Name lets JustIce work standalone. If you get a "java.lang.OutOfMemoryError", you should increase the maximum Java heap space. A command like java -Xmx1887436800 org.apache.bcel.verifier.Verifier f.q.c.Name will usually resolve the problem. The value above is suitable for big server machines; if your machine starts swapping to disk, try to lower the value. Running a graphics based verifier If you prefer a graphical application, you should use a command like java org.apache.bcel.verifier.GraphicalVerifier to launch one. Again, you may have to resolve a memory issue depending on the classes to verify. Contact If you spot a bug in the BCEL or its accompanying verifier "JustIce" please check with the BCEL mailing list http://jakarta.apache.org/bcel or enter the issue into the BCEL bug database http://issues.apache.org/bugzilla/enter_bug.cgi?product=BCEL