import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class TanpaMerge {

    record Produk(String nama, String kategori, int harga) {}

    public static void main(String[] args) {
        List<Produk> etalase = List.of(
            new Produk("Pena", "alat tulis", 2000),
            new Produk("Pena", "alat tulis", 2500)
        );

        // TANPA merge function: kunci ganda memicu IllegalStateException
        Map<String, Integer> harga = etalase.stream()
            .collect(Collectors.toMap(Produk::nama, Produk::harga));
        System.out.println(harga);
    }
}