📂 InventorySystem  
├── 📄 Product.java (Class Model)  
├── 📄 InventoryManager.java (Class Logic)  
└── 📄 MainApp.java (GUI Main Class)

public class Product {
    private String id;
    private String name;
    private double price;
    private int stock;

    // Constructor
    public Product(String id, String name, double price, int stock) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.stock = stock;
    }

    // Getter & Setter
    public String getId() { return id; }
    public String getName() { return name; }
    public double getPrice() { return price; }
    public int getStock() { return stock; }

    public void setStock(int stock) { this.stock = stock; }
}

import java.util.ArrayList;
import java.util.List;

public class InventoryManager {
    private List<Product> products = new ArrayList<>();

    // Tambah produk baru
    public void addProduct(Product product) {
        products.add(product);
    }

    // Hapus produk
    public boolean removeProduct(String id) {
        return products.removeIf(p -> p.getId().equals(id));
    }

    // Cari produk
    public Product findProduct(String keyword) {
        return products.stream()
                .filter(p -> p.getId().equals(keyword) || p.getName().equalsIgnoreCase(keyword))
                .findFirst()
                .orElse(null);
    }

    // Update stok
    public void updateStock(String id, int newStock) {
        Product product = findProduct(id);
        if (product != null) {
            product.setStock(newStock);
        }
    }

    // Dapatkan semua produk
    public List<Product> getAllProducts() {
        return products;
    }
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;

public class MainApp extends JFrame {
    private InventoryManager manager = new InventoryManager();
    private JTable table;
    private JTextField idField, nameField, priceField, stockField;

    public MainApp() {
        setTitle("Sistem Inventaris Toko Retail");
        setSize(800, 500);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        // Form Input
        JPanel inputPanel = new JPanel(new GridLayout(4, 2, 10, 10));
        idField = new JTextField();
        nameField = new JTextField();
        priceField = new JTextField();
        stockField = new JTextField();

        inputPanel.add(new JLabel("Kode Barang:"));
        inputPanel.add(idField);
        inputPanel.add(new JLabel("Nama Barang:"));
        inputPanel.add(nameField);
        inputPanel.add(new JLabel("Harga:"));
        inputPanel.add(priceField);
        inputPanel.add(new JLabel("Stok:"));
        inputPanel.add(stockField);

        // Tombol Aksi
        JButton addButton = new JButton("Tambah");
        JButton deleteButton = new JButton("Hapus");
        JButton searchButton = new JButton("Cari");

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(addButton);
        buttonPanel.add(deleteButton);
        buttonPanel.add(searchButton);

        // Tabel Data
        String[] columns = {"Kode", "Nama", "Harga", "Stok"};
        table = new JTable(new Object[0][4], columns);
        JScrollPane scrollPane = new JScrollPane(table);

        // Layout
        add(inputPanel, BorderLayout.NORTH);
        add(scrollPane, BorderLayout.CENTER);
        add(buttonPanel, BorderLayout.SOUTH);

        // Event Listeners
        addButton.addActionListener(this::addProduct);
        deleteButton.addActionListener(this::deleteProduct);
        searchButton.addActionListener(this::searchProduct);
    }

    private void addProduct(ActionEvent e) {
        try {
            String id = idField.getText();
            String name = nameField.getText();
            double price = Double.parseDouble(priceField.getText());
            int stock = Integer.parseInt(stockField.getText());

            manager.addProduct(new Product(id, name, price, stock));
            refreshTable();
            JOptionPane.showMessageDialog(this, "Produk berhasil ditambahkan!");
        } catch (NumberFormatException ex) {
            JOptionPane.showMessageDialog(this, "Input tidak valid!", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }

    private void deleteProduct(ActionEvent e) {
        String id = JOptionPane.showInputDialog(this, "Masukkan Kode Barang:");
        if (id != null && manager.removeProduct(id)) {
            refreshTable();
            JOptionPane.showMessageDialog(this, "Produk dihapus!");
        } else {
            JOptionPane.showMessageDialog(this, "Produk tidak ditemukan!", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }

    private void searchProduct(ActionEvent e) {
        String keyword = JOptionPane.showInputDialog(this, "Cari (Kode/Nama):");
        Product product = manager.findProduct(keyword);
        if (product != null) {
            JOptionPane.showMessageDialog(this, 
                "Hasil Pencarian:\n" +
                "Kode: " + product.getId() + "\n" +
                "Nama: " + product.getName() + "\n" +
                "Harga: " + product.getPrice() + "\n" +
                "Stok: " + product.getStock());
        } else {
            JOptionPane.showMessageDialog(this, "Produk tidak ditemukan!", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }

    private void refreshTable() {
        List<Product> products = manager.getAllProducts();
        Object[][] data = new Object[products.size()][4];
        for (int i = 0; i < products.size(); i++) {
            Product p = products.get(i);
            data[i] = new Object[]{p.getId(), p.getName(), p.getPrice(), p.getStock()};
        }
        table.setModel(new javax.swing.table.DefaultTableModel(data, new String[]{"Kode", "Nama", "Harga", "Stok"}));
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new MainApp().setVisible(true));
    }
}