i am gettin an error in this line mArrayAdapter.add(device.getName() + "\n" + device.getAddress());

package com.example.i.t;

import java.util.Set;

import android.support.v7.app.ActionBarActivity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;


public class MainActivity extends ActionBarActivity {

    private static final int REQUEST_ENABLE_BT = 0;
	private static final Set<bluetoothdevice> mArrayAdapter = null;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        runfyita();
        
        
        runfyitb();
        
        bluetoothadapter();
        
        
        
    }
	
private void bluetoothadapter() {
		// TODO Auto-generated method stub
    	
            BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
            
            if (!mBluetoothAdapter.isEnabled())
            	
            { 
            	 Intent enableBtIntent = new Intent (BluetoothAdapter.ACTION_REQUEST_ENABLE);
            	 
            	 startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
            	 
            	 Set<bluetoothdevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
            	 
            	 if (pairedDevices.size() > 0)
            	 {
            		  for (BluetoothDevice device : pairedDevices)
            		  {
            			mArrayAdapter.add(device.getName() + "\n" + device.getAddress());

            		  }
            	 }
            	 
            	 
            	 final BroadcastReceiver mReceiver = new BroadcastReceiver() {
					
					@Override
					public void onReceive(Context context, Intent intent) {
						// TODO Auto-generated method stub
						
						String action = intent.getAction();
						
						if (BluetoothDevice.ACTION_FOUND.equals(action))
						{
							
							BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
							
							 mArrayAdapter.add(device.getName() + "\n" + device.getAddress());

						}
						
					}
				};

            }
		
	}












	private void runfyitb() {
		// TODO Auto-generated method stub
    	
    	Button button = (Button) findViewById(R.id.fyitb);
    	
    	button.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				
				Intent intent = new Intent (MainActivity.this, Fyitbtimetable.class);
				
				startActivity(intent);
				
				
				
			}
		});
		
	}


private void runfyita() {
		// TODO Auto-generated method stub
		
		
		Button button = (Button) findViewById(R.id.fyita);
		
		button.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				
				Intent intent = new Intent(MainActivity.this, Fyitatimetable.class);
				
				startActivity(intent);
				
			}
		});
	}



@Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}