change activity in android studio code example

Example 1: intent android open activity

Intent intent = new Intent(this, DisplayMessageActivity.class);
        intent.putExtra(key:,value:);
        startActivity(intent);

Example 2: android how to switch between activities

Intent intent = new Intent(getApplicationContext(), ActivityToBeOpened.class);
startActivity(intent);

Example 3: change fragment in android studio

// put the following code in onClickListner
// public void onClickListner(View view){
Navigation.findNavController(view).navigate(R.id.action_fromFragment_toFragment);
// action_fromFragment_toFragment is the id of transformatino, look in fragment map.
// }