Passing a string from one activity to another and adding it on a edittext

i am trying to send one string from one activity to another and posting it on a edittext field I have googled a lot but i couldn't find anything (maybe its my fault)

Here is the code MainActivity (with the string)

public class MainActivity extends ActionBarActivity {
    private Button mbutton;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final String go="send?";
        final Context context=this;
        mbutton = (Button)findViewById(R.id.hello);
        mbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {


                Intent intent=new Intent(context, work.class);
                intent.putExtra("contents", go);
                startActivity(intent);
            }
        });
    }
}

My second activity

public class work extends Activity {
    EditText codeTxt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        codeTxt = (EditText) findViewById(R.id.txtCode);

        Bundle extras = getIntent().getExtras();
        final String dam= extras.getString("contents");
        codeTxt.setText(dam);
    }
}

I get this app as stope working after pressing the button Keep in mind that this is just a draft to learn who to do this to use in other app.