function int FSAL(){ return 100; }

rule insFirst
salience ( FSAL )  ## Oops, forgot the parens...
when
then
end

Exception in thread "main" org.drools.RuntimeDroolsException: Unexpected exception executing action org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction@354749
	at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:996)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:730)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:699)
	at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218)
	at express.Main.execute(Main.java:71)
	at express.Main.main(Main.java:93)
Caused by: java.lang.ClassCastException: org.mvel2.util.MethodStub cannot be cast to java.lang.Number
	at org.drools.base.mvel.MVELSalienceExpression.getValue(MVELSalienceExpression.java:86)
	at org.drools.reteoo.RuleTerminalNode.assertLeftTuple(RuleTerminalNode.java:215)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:189)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:138)
	at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:141)
	at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:59)
	at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:185)
	at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:143)
	at org.drools.reteoo.Rete.assertObject(Rete.java:107)
	at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:260)
	at org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:343)
	at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:994)
	... 5 more