android - Bengali unicoded character showing problem

I have created an android application where I want to display unicoded bengali sentences.
For this I have done the following steps.

Step1: I store my bengali font named Siyamrupali.ttf in the Assets folder.

Step2: In main.xml file I took a text view where I display characters.

Step3: In my MainActivity. Java I wrote this...

public class mainAc extends Activity 

{

    AssetManager arabi_font;

    TextView tx;
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        tx=(TextView)findViewById(R.id.tv);
        try
        {
            String str="\u0986";
            tx.setTypeface(Typeface.createFromAsset(getAssets(),"Siyamrupali.ttf"));
            tx.setText(str);    
        }
        catch(Exception ex)
        {
            tx.setText("font cannot load: "+ ex.toString() );

        }   
    }

Then output show আ Which one is correct But When i wrote String str="\u0986\u09AE\u09Bf";
In MainActivity. Java

Then output shows আমই But i should be আমি

What can I do now to solve this problem. Any body give me some advice or link or sample code.