Put SQL statement into a method

I have a repeated resultset object that I use alot to execute a
statement that fetches max id from a table.

I was wondering if I can put it in a method and call the method each
time I need the max id?

The repeated part is:
Resultset rs = statement.executeQuery("select max(id) from
TableMain");
rs.next();

Here is an example of what I am doing now:

CODE
Statement statement = connection.createStatement();
if(condition here..)
{
    Resultset rs = statement.executeQuery("select max(id) from
TableMain");
    rs.next();
    a = rs.getInt(1);
    //my insert sql is here to insert into another table the value of
the max id....

//another call to get the max id:
if(another condition here...)
{
    Resultset rs = statement.executeQuery("select max(id) from
TableMain");
    rs.next();
    c = rs.getInt(1);
   //my insert sql is here to insert into another table the value of
the max id....

I need help on my attempt below because I am not sure how to do it.
My attempts keep giving me zero for max id or I dont fetch anything.
Please advise.

public ResultSet getMaxId()
{
         Resultset rs = statement.executeQuery("select max(id) from
TableMain");
         rs.next();
         return rs;
}

Call it like this:

if(any condition here..)
{
    getMaxId();
    f = rs.getInt(1);
   ///my insert sql is here to insert into another table the value of
the max id....