NPE friendAdapter.getCheckedItems(); in android

Hi in the below code I am getting the NPE at the line `friendAdapter.getCheckedItems();'.Actually I want only checked values From checkbox.

And Then I want to pass the selected values I want to return as array and passed as parameter to the method createGroup()

Can any one help me. Why i am getting this error

java

public class GroupList extends ListActivity 
{       
    boolean[] checkBoxState;
    boolean isChecked;
    String[] check;
    String[] mStringArray;
    ListView users;
    int position;
    int i;
    private IAppManager imService = null;

    private FriendListAdapter friendAdapter;

    public String ownusername = new String();

    private class FriendListAdapter extends BaseAdapter 
    {   
        @SuppressWarnings("unused")

        class ViewHolder {
            TextView text;
            ImageView icon;
            CheckBox check1;



        }

        private LayoutInflater mInflater;
        private Bitmap mOnlineIcon;
        private Bitmap mOfflineIcon;        

        private FriendInfo[] friend = null;





        public FriendListAdapter(Context context) {
            super();            

            mInflater = LayoutInflater.from(context);

            mOnlineIcon = BitmapFactory.decodeResource(context.getResources(), R.drawable.greenstar);
            mOfflineIcon = BitmapFactory.decodeResource(context.getResources(), R.drawable.redstar);

        }

        public void setFriendList(FriendInfo[] friends)
        {
            this.friend = friends;

        }


        public int getCount() {     

            return friend.length;
        }


        public FriendInfo getItem(int position) {           

            return friend[position];
        }

        public long getItemId(int position) {

            return 0;
        }
        public ArrayList<FriendInfo> getCheckedItems(){
            ArrayList<FriendInfo> result = new ArrayList<FriendInfo>();
            for (int i = 0; i < checkBoxState.length; i++) {
                 if(checkBoxState[i]){
                     result.add(getItem(i));
                     System.out.print(result);
                 }
            }
            return result;

        }
        public View getView(final int position, View convertView, ViewGroup parent) {

            final ViewHolder holder;


            if (convertView == null) 
            {
                convertView = mInflater.inflate(R.layout.grouplist, null);


                holder = new ViewHolder();

                holder.text = (TextView) convertView.findViewById(R.id.text);
                holder.icon = (ImageView) convertView.findViewById(R.id.icon);
                holder.check1 = (CheckBox)convertView.findViewById(R.id.checkBox1);

                convertView.setTag(holder);

            }           

            else {

                holder = (ViewHolder) convertView.getTag();

            }


            holder.text.setText(friend[position].userName);
            holder.icon.setImageBitmap(friend[position].status == STATUS.ONLINE ? mOnlineIcon : mOfflineIcon);

            //final ArrayList<String> checkedFriends = new ArrayList<String>();
            checkBoxState = new boolean[friend.length];
            holder.check1.setChecked(checkBoxState[position]);
            holder.check1.setOnCheckedChangeListener(new OnCheckedChangeListener(){

                public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                    checkBoxState[position]=isChecked;


                }
            });

            return convertView;
        }


    }
    protected void onCreate(Bundle savedInstanceState) 
    {       
        super.onCreate(savedInstanceState);
        if (android.os.Build.VERSION.SDK_INT > 9) {
            StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
            .permitAll().build();
            StrictMode.setThreadPolicy(policy);
        }
        setContentView(R.layout.group_list_screen);

        Button create=(Button)findViewById(R.id.create);

        friendAdapter.getCheckedItems();
        create.setOnClickListener(new OnClickListener() {

            @SuppressWarnings({ "unused", "unchecked" })
            @Override
            public void onClick(View v) {
                String groupname = getIntent().getStringExtra("nick");

                            try {

                                String result1 = imService.CreateGroup(groupname,imService.getUsername(),check);
                            } catch (UnsupportedEncodingException e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }       

                Toast.makeText(getApplicationContext(), "Group Created Sucessfully",Toast.LENGTH_LONG).show();  
            }
        });   
        friendAdapter = new FriendListAdapter(this);
    }