how to use autonumber in java netbeans?

void notrans(){
// this is my function :
try{
    
    String sql="select right(No_Trans,2) as no_akhir from jual";
    Statement stat=conn.createStatement();
    ResultSet res=stat.executeQuery(sql);
    if(res.first()==false){
        txttrans.setText("TRX0001");
    }else{ 
        res.last(); 
        int no=res.getInt(1)+1;
        String cno=String.valueOf(no);
        int pjg_cno=cno.length();
        for(int i=0;i<2-pjg_cno;i++){
           cno="00"+cno;
    }
    txttrans.setText("TRX00"+cno);
}
}catch(Exception e ){
}
}