What methods can be used to implement data exchange between two Activities in an application?

Data exchange between two Activities in Android can be implemented in several ways:

1. Via Intent — when launching the second Activity, data can be passed through extras:

Intent intent = new Intent(this, SecondActivity.class);
intent.putExtra("key", "value");
startActivity(intent);

The second Activity retrieves data from the Intent.

2. startActivityForResult — if you need to get a result back:

// In the first Activity
Intent intent = new Intent(this, SecondActivity.class);
startActivityForResult(intent, REQUEST_CODE);

// In the second Activity
Intent resultIntent = new Intent();
resultIntent.putExtra("resultKey", "resultValue");
setResult(RESULT_OK, resultIntent);
finish();

3. Using shared storage — for example, SharedPreferences, databases, or singleton classes for storing data accessible to both Activities.

4. Via ViewModel and LiveData (if using MVVM architecture with Jetpack) — for data exchange between Activities and fragments.

The method choice depends on the task and the application's architecture.