Question

I currently have an ArrayList holding objects of a class I have created, I then parse through the ArrayList in a for loop searching and comparing some data from the ArrayList and some global variables that are loaded else where, however this ArrayList is constantly growing and will eventually have about 115 elements to it towards the end, which then takes a very long time to search through, the function that does this is also called once for every line I read from a text file and the text file will usually be around 400-500 lines long so as you can tell it is very slow process even when testing on small files. Is there a way to speed this up by maybe using another collection instead of an ArrayList, my reasoning for using the ArrayList is I have to know what index it is on when it finds a match.

Here is the class:

private ArrayList<PanelData> panelArray = new ArrayList<PanelData>(1);

    public class PanelData {
        String dev = "";
        String inst = "";
        double tempStart = 0.0;
        double tempEnd = 0.0;
    }

Function:

public void panelTimeHandler (double timeStart, double timeEnd) throws SQLException {   
        PanelData temps = new PanelData();
        temps.dev = devIDStr;
        temps.inst = instanceStr;
        temps.tempStart = timeStart;
        temps.tempEnd = timeEnd;
        boolean flag = false;

        if(!flag)
        {
            panelArray.add(temps);
            flag = true;
        }

        for(int i = 0; i < panelArray.size(); ++i ) {
            if(panelArray.get(i).dev.equals(devIDStr) && panelArray.get(i).inst.equals(instanceStr)) {
                if(panelArray.get(i).tempStart <= timeStart  && panelArray.get(i).tempEnd >= timeEnd ) {
                    //Do Nothing
                }
                else 
                {
                    temps.dev = devIDStr;
                    temps.inst = instanceStr;
                    temps.tempStart = timeStart;
                    temps.tempEnd = timeEnd;
                    insert();
                    panelArray.set(i, temps);
                }
            }
            else
            {
                temps.dev = devIDStr;
                temps.inst = instanceStr;
                temps.tempStart = timeStart;
                temps.tempEnd = timeEnd;
                panelArray.add(temps);
                insert();
            }
        }
    }

If there is something more you would like to see just ask, thanks. Beef.

Update: Added insert() function

private void insert() throws SQLException
{
    stmt = conn.createStatement();  

    String sqlStm = "update ARRAY_BAC_SCH_Schedule set SCHEDULE_TIME = {t '" + finalEnd + "'} WHERE SCHEDULE_TIME >=  {t '" + finalStart + "'} AND" +
        " SCHEDULE_TIME <=  {t '" + finalEnd + "'} AND VALUE_ENUM = 0 AND DEV_ID = " + devIDStr + " and INSTANCE = " + instanceStr;
    int updateSuccess = stmt.executeUpdate(sqlStm);

    if (updateSuccess < 1)
    {   
        sqlStm = "insert into ARRAY_BAC_SCH_Schedule (SITE_ID, DEV_ID, INSTANCE, DAY, SCHEDULE_TIME, VALUE_ENUM, Value_Type) " +
                " values (1, " + devIDStr + ", " + instanceStr + ", " + day + ", {t '" + finalStart + "'}, 1, 'Unsupported')";
        stmt.executeUpdate(sqlStm);
        sqlStm = "insert into ARRAY_BAC_SCH_Schedule (SITE_ID, DEV_ID, INSTANCE, DAY, SCHEDULE_TIME, VALUE_ENUM, Value_Type) " +
                " values (1," + devIDStr + ", " + instanceStr + ", " + day + ", {t '" + finalEnd + "'}, 0, 'Unsupported')";
        stmt.executeUpdate(sqlStm);
    }
    if(stmt!=null)
        stmt.close();
}

Update:

Thank you to Matteo, I realized I was adding to the array even if I didnt find a match till the 10th element it would then added to the array the first 9 times which created many extra elements in the array, which was why it was so slow, I added some breaks and did a little tweaking in the function, and it improved the performance a lot. Thanks for all the input

Answer 1

What about using a hashmap?

I would create a small class for the key:

class Key {
  String dev, instr;

  // todo: implements equals & hashCode
}

and create the map:

Map<Key, PanelData> map = new HashMap...

then you can easily find the element you need by invoking map.get(new Key(...)).

Instead of creating a new class, you could also tweak the PanelData class, implementing methods equals & hashcode so that two classes are equal iff their dev and instr are equal. In this case, your map becomes:

Map<PanelData, PanelData> map ...

// to add:
map.put(temps, temps)

// to search:
PanelData elem = map.get(new PanelData(desiredDev, desiredInstr));