startActivityForResult() sample code

Activity2.java

public class Activity2 extends AppCompatActivity {

    public static final String RESULT = "result";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_2);
        Bundle bundle = getIntent().getExtras();
        if (bundle != null) {
            String messageFromActivity = bundle.getString(MESSAGE);
            if (messageFromActivity != null && messageFromActivity.length() >= 3) {
                String response = "Yes, I'm here";

                Intent intent = new Intent();
                intent.putExtra(RESULT, response);
                setResult(RESULT_OK, intent);

                finish();
            }
        }
    }
}