sql="update Users set PostNumber='"+postnum+"' where UserName='"+username+"'";
System.out.println("44");
statement.executeQuery(sql);
System.out.println("55");
sql="update Users set PostNumber='"+postnum+"' where UserName='"+username+"'";
System.out.println("44");
if(statement.executeQuery(sql)){
System.out.println("55");}
这样试试
sql="update Users set PostNumber='"+postnum+"' where UserName='"+username+"'";
System.out.println("44");
if(statement.executeUpdate(sql)){
System.out.println("55");}