Product.java

public class Product {
    private int productId;
    private String productName;
    private double price;

    public int getProductId()             { return productId; }
    public String getProductName()        { return productName; }
    public double getPrice()              { return price; }

    public void setProductId(int id)      { this.productId = id; }
    public void setProductName(String n)  { this.productName = n; }
    public void setPrice(double price) {
        if (price >= 0) { this.price = price; }
        else { System.out.println("Error: Price cannot be negative!"); }
    }

    public void displayProduct() {
        System.out.println("--- Product Details ---");
        System.out.println("Product ID   : " + getProductId());
        System.out.println("Product Name : " + getProductName());
        System.out.println("Price        : Rs. " + getPrice());
    }
}