public class SelectItemService SelectItemVisitor{
...override
@Override
public void visit(SelectExpressionItem selectExpressionItem){
 Expression expression = selectExpressionItem.getExpression();
 if (expression instance CaseExpression){
 CaseExpression caseExpression = (CaseExpression) expression;
 for (WhenClause whenClause : caseExperssion.getWhenClause()){
 Expression whenExpression = whenClause.getWhenExpression();
 whenExpression.accept(new ExpressionService());
 }
 }
 }
}
public class ExpressionService implements ExpressionVisitor {
...override
 @Override
 public void visit(CaseExpression caseExpression){
 List<WhenClause> whenClauses = caseExpression.getWhenClauses();
 for (WhenClause whenClause : whenClauses){
 Expression whenExpression = whenClause.getWhenExpression();
 
 if (whenExpression instanceof LikeExpression){
 // ignore other visit(....) 
 whenExpression.accept(this); 
 String leftExp = ((LikeExpression) whenExpression).getLeftExpression().toString();
 String rightExp = ((LikeExpression) whenExpression).getRightExpression().toString();
 // here I'm assuming that these two result are the same
 // how can i replace the caseExpression to (Expression)LongValue or other Expression?
 ......
 } 
 }
 }
}