@Test
   public void exampleSelectingRegularEmployeesUsingTypeKeyword(){
      List<RegularEmployee> regularEmployees = createRegularEmployees(2);
      List<ContractorEmployee> contractorEmployees = createContractorEmployees(3);

      
      em.getTransaction().begin();
      for(RegularEmployee e:regularEmployees){
         em.persist(e);
      }
      for(ContractorEmployee e:contractorEmployees){
         em.persist(e);
      }
      em.getTransaction().commit();
      
      Query query = em.createQuery("SELECT e FROM Employee WHERE TYPE(e)<>RegularEmployee");
      @SuppressWarnings("unchecked")
      List<RegularEmployee> regularEmployeesReturned = query.getResultList();
      assertEquals(regularEmployees.size(), regularEmployeesReturned.size());
   }

java.lang.NullPointerException
   at org.hibernate.hql.internal.ast.tree.MethodNode.typeDiscriminator(MethodNode.java:86)
   at org.hibernate.hql.internal.ast.tree.MethodNode.resolve(MethodNode.java:67)
   at org.hibernate.hql.internal.ast.HqlSqlWalker.processFunction(HqlSqlWalker.java:1008)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.functionCall(HqlSqlBaseWalker.java:2612)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.expr(HqlSqlBaseWalker.java:1338)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.exprOrSubquery(HqlSqlBaseWalker.java:4426)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.comparisonExpr(HqlSqlBaseWalker.java:3922)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.logicalExpr(HqlSqlBaseWalker.java:2076)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.whereClause(HqlSqlBaseWalker.java:794)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:595)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:299)
   at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:247)
   at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:250)
   at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:185)
   at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:138)
   at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:105)
   at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
   at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:168)
   at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:221)
   at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:199)
   at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1784)
   at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:291)
   at ro.scutaru.trainingjpa.employee.domain.EmployeeInheritanceTest.exampleSelectingRegularEmployeesUsingTypeKeyword(EmployeeInheritanceTest.java:49)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
   at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
   at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
   at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
   at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
   at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
   at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
   at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
   at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
   at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
   at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
   at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
   at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
   at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
   at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
   at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "EMP_TYPES")
public class Employee {
....