Android Performance of Listview

package com.myapp;

import java.util.ArrayList;
import java.util.HashMap;

import android.os.Bundle;
import android.app.Activity;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity  {
	
	ArrayList<HashMap<String, String>> MyArrList;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
       
        // listView1
        final ListView lisView1 = (ListView)findViewById(R.id.listView1); 
        	
		MyArrList = new ArrayList<HashMap<String, String>>();
		HashMap<String, String> map;
		
		/*** Rows 1 ***/
		map = new HashMap<String, String>();
		map.put("ID", "1");
		map.put("Code", "TH");
		map.put("Country", "Thailand");
		MyArrList.add(map);
		
		/*** Rows 2 ***/
		map = new HashMap<String, String>();
		map.put("ID", "2");
		map.put("Code", "VN");
		map.put("Country", "Vietnam");
		MyArrList.add(map);	
		
		/*** Rows 3 ***/
		map = new HashMap<String, String>();
		map.put("ID", "3");
		map.put("Code", "ID");
		map.put("Country", "Indonesia");
		MyArrList.add(map);	
		
		/*** Rows 4 ***/
		map = new HashMap<String, String>();
		map.put("ID", "4");
		map.put("Code", "LA");
		map.put("Country", "Laos");
		MyArrList.add(map);	
		
		/*** Rows 5 ***/
		map = new HashMap<String, String>();
		map.put("ID", "5");
		map.put("Code", "MY");
		map.put("Country", "Malaysia");
		MyArrList.add(map);		
       
		lisView1.setAdapter(new CountryAdapter(this));
		
    }
    
    public class CountryAdapter extends BaseAdapter 
    {
        private Context context;

        public CountryAdapter(Context c) 
        {
        	// TODO Auto-generated method stub
            context = c;
        }
 
        public int getCount() {
        	// TODO Auto-generated method stub
            return MyArrList.size();
        }

 
        public Object getItem(int position) {
        	// TODO Auto-generated method stub
            return position;
        }
 
        public long getItemId(int position) {
        	// TODO Auto-generated method stub
            return position;
        }

		public View getView(final int position, View convertView,
				ViewGroup parent) {
			// TODO Auto-generated method stub
			CountryHolder holder = null;

			if (convertView == null) {
				
				LayoutInflater inflater = (LayoutInflater) context
						.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
				 convertView = inflater.inflate(R.layout.activity_column, null);

				holder = new CountryHolder();
				holder.ID = (TextView) convertView.findViewById(R.id.ColID);
				holder.Code = (TextView) convertView.findViewById(R.id.ColCode);
				holder.Country = (TextView) convertView.findViewById(R.id.ColCountry);

				convertView.setTag(holder);
			} else {
				holder = (CountryHolder) convertView.getTag();
			}

	        holder.ID.setText(MyArrList.get(position).get("ID"));
	        holder.Code.setText(MyArrList.get(position).get("Code"));
	        holder.Country.setText(MyArrList.get(position).get("Country"));
	        
			return convertView;

		}

    }
    
	public class CountryHolder {
		TextView ID;
		TextView Code;
		TextView Country;
	}

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    
}