Create simple program which show the use of spinners, using Java in Android Studio.

Java Code: -

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {

    Spinner spinner;
    String[] words = {"Hello", "Bye", "Welcome", "Hi"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        spinner = findViewById(R.id.spinner_id);
        spinner.setOnItemSelectedListener(this);

        ArrayAdapter<String> data = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, words);
        data.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(data);
    }

    @Override
    public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long id) {
        Toast.makeText(getApplicationContext(), words[position], Toast.LENGTH_LONG).show();
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }
}

XML Code: -

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Spinner
        android:id="@+id/spinner_id"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>