Example1.java

// MainActivity.java
private void onSomeItemSelected(Item item) {
    Intent intent = new Intent(this, SomeAwesomeAndHyperRealisticDetailActivity.class);
    intent.putExtra(SomeAwesomeAndHyperRealisticDetailActivity.EXTRA_ITEM_ID, "id");
    intent.putExtra(SomeAwesomeAndHyperRealisticDetailActivity.EXTRA_WANNA_SHOW, true);
    startActivity(intent);
}

// SomeAwesomeAndHyperRealisticDetailActivity.java
public static String EXTRA_ITEM_ID = "EXTRA_ITEM_ID";
public static boolean EXTRA_WANNA_SHOW = "EXTRA_WANNA_SHOW";

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ....
    Bundle bundle = getIntent().getExtras();
    if (bundle != null) {
        String id = bundle.getString(EXTRA_ITEM_ID);
        if (id == null) {
            throw new IllegalStateException();
        } else {
            boolean wannaShow = bundle.getBoolean(EXTRA_WANNA_SHOW, false);
            loadData(id);
        }
    } else {
        throw new IllegalStateException();
    }
    ....
}