// Inside the first activity using the intent that will start the second activity:
// # see switchActivity.java
intent.putExtra("$Key$",$value$);

// Inside the second activity:
Bundel extras = getIntent().getExtras();
if (extras != null)
{
    String messageReceived = extras.getString("$Key$");
    int intReceived = extras.getInt("$Key$");
}