String getAccCodeFromNewYearSql="select acc_code from A where year=2016"
String getAccCodeFromOldYearSql="select acc_code from A where year=2015"
stmt=connOld.prepareStatement(getAccCodeFromOldYearSql);
ResultSet oldrs=stmt.executeQuery();
stmt=connOld.prepareStatement(getAccCodeFromNewYearSql);
ResultSet newrs=stmt.executeQuery();
//得到这两个ResultSet 后 如何对比里面的acc_code,查出新年度比旧年度多了哪些acc_code.