slow iterator

[jamborta]

hi there,
I am trying to write a small method that generates a mysql command. but it looks like that this method uses 98% of the running time. I can't make it faster. I tried hashmap instead of arraylist, different iterators, no result.

    public void test (int id, ArrayList<Integer> link){
        String mySqlCommand = "INSERT INTO profiles_child (userid, link) VALUES";
        for(int i=0;i<link.size();i++){
            if (id != link.get(i))
            mySqlCommand += "("+id+","+link.get(i)+"),";
        }
        mySqlCommand = mySqlCommand.substring(0, mySqlCommand.length()-1); //removing last character
        mySqlCommand += ";";
        addToDatabaseLink1(mySqlCommand);

    }

thanks a lot.
Tom

[Fubarable]

My guess is that the problem has nothing to do with the iteration and everything to do with the last method call above:
addToDatabaseLink1(...).

If you really want to know what is slowing you down, perhaps you can get your hands on a profiler. NetBeans I think has one in its IDE, and perhaps Eclipse does too, but I'm not sure.

[jamborta]

actually the profiler says that this method uses most of the rescources, especially when it is dealing with a long arraylist...

[Fubarable]

Yes, but what part of this method? Again, I suggest that it's the part at the bottom and has nothing to do with iteration.

The only other thought I have (for what they are worth), if you find that it is the loop causing the problem then to use a StringBuilder here and not do String concatonation directly.

[jamborta]

thanks a lot. stringbuilder sorted out the problem.

[Fubarable]

cool. You must be iterating through a lot of strings then.

[Eranga]

Best way to findout this, write a simple code for concatenation and compile it with the verbose option. Just for a single concatenation operation in String class and the StringBuilder, approximately you can see 10~20ms difference.

[Supamagier]

Isn't a String compiled to a StringBuilder anyway? So what use would it be to replace String with StringBuilder in your code?

[Fubarable]

Isn't a String compiled to a StringBuilder anyway? So what use would it be to replace String with StringBuilder in your code?

I think it has something to do with reducing the number of objects created within the loop.

[RamyaSivakanth]

Hi,
One small suggestion is u can use PreparedStatement.No need to build n number of string like this.

1.just declare the query string as final and using preparestatement and set the values for userid and link.

final String insertQuery = "INSERT INTO PROFILES_CHILD (USERID, LINK) VALUES ( ?,?)";


-Regards
Ramya