Question

What is the most efficient way to search a list of objects and also increment one of its variables? Also addData() function call 10000 time and in this list have max 30 diff-diff key with increment variable .

Thanks,

public void addData(List<DataWise> wise ,String name) 
    {
        if(wise!=null)
        {

            for (DataWise dataWise : wise) {

                if(dataWise.getName().equals(name))
                {
                    dataWise.setVisits(1);
                    return;
                }
            }
        }
        DataWise dataWise2=new DataWise(name,1);
        wise.add(dataWise2);
    }

public class DataWise 
{

    private String name;
    private int visits;

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getVisits() {
        return visits;
    }
    public void setVisits(int visits) {
        this.visits+= visits;
    }
}

Answer 1

If it’s guarantteed that the name of each DataWise is unique in the list, use a HashMap<String, DataWise>, where the String key is the name of the DataWise. This will lead to O(1) instead of O(n):

Map<String, DataWise> map = new HashMap<String, DataWise>();
...
DataWise wise = map.get(name);
if (wise != null) {
    wise.incrementVisits();
}
else {
    wise = new DataWise(name, 1);
    map.put(name, wise);
}

Note that a setter (setVisits()) should set the visits value to the value of the argument. Incrementing the number of visits is really counter-intuitive. This is why I used an incrementVisits method, which is much clearer.