(2）实例化集合类（用反射的方式完成实例化〉(1）定义商品类
(2）实例化集合类（用反射的方式完成实例化〉v
(3）功能1:遍历集合显示出商品信息（商品编号从小到大)。
(4）功能2:查找各种类别，最高和最低商品。(stream Collections)。
(5)功能3:增加一个商品到集合（编号不能重复，要做处理)
(6）功能4:删除指定编号的商品，不存在有提示
(7）功能5:退出或因异常程序要退出的时候，开启线程将集合序列化到product..ser.文件中。下次运行时候读取 product.er.反序列化得到集合，并能在此基础上继续进行增加或删除数据。
(8）功能6:有功能菜单，可以反复选择上述功能。v
(9)功能7:筛选食品类别中价格最高的前3个商品,并遍历显示商品信息。(用stream)。
(10）功能8: Scanner输入的异常要求处理，不要中止程序。
引用 皆我百晓生 小程序回复内容作答：
下面是一个示例代码，实现了上述功能：
import java.io.*;
import java.util.*;
import java.lang.reflect.*;
class Product implements Serializable {
private int id;
private String name;
private String category;
private double price;
public Product(int id, String name, String category, double price) {
this.id = id;
this.name = name;
this.category = category;
this.price = price;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public String getCategory() {
return category;
}
public double getPrice() {
return price;
}
@Override
public String toString() {
return "Product{" +
"id=" + id +
", name='" + name + '\'' +
", category='" + category + '\'' +
", price=" + price +
'}';
}
}
public class Main {
private static List<Product> products = new ArrayList<>();
private static String fileName = "product.ser";
public static void main(String[] args) {
loadProducts();
displayMenu();
}
private static void loadProducts() {
try {
File file = new File(fileName);
if (file.exists()) {
FileInputStream fis = new FileInputStream(file);
ObjectInputStream ois = new ObjectInputStream(fis);
products = (List<Product>) ois.readObject();
ois.close();
fis.close();
System.out.println("Products loaded from " + fileName);
}
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
}
}
private static void saveProducts() {
try {
FileOutputStream fos = new FileOutputStream(fileName);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(products);
oos.close();
fos.close();
System.out.println("Products saved to " + fileName);
} catch (IOException e) {
e.printStackTrace();
}
}
private static void displayMenu() {
Scanner scanner = new Scanner(System.in);
int choice;
do {
System.out.println("Please choose an option:");
System.out.println("1. Display products");
System.out.println("2. Find highest and lowest priced products");
System.out.println("3. Add a product");
System.out.println("4. Remove a product");
System.out.println("5. Save and exit");
System.out.println("6. Filter top 3 most expensive food products");
System.out.println("0. Exit");
try {
choice = scanner.nextInt();
scanner.nextLine(); // Consume new line character
switch (choice) {
case 1:
displayProducts();
break;
case 2:
findHighestAndLowestPricedProducts();
break;
case 3:
addProduct(scanner);
break;
case 4:
removeProduct(scanner);
break;
case 5:
saveProducts();
System.out.println("Exiting...");
return;
case 6:
filterTop3ExpensiveFoodProducts();
break;
case 0:
System.out.println("Exiting...");
return;
default:
System.out.println("Invalid choice. Please try again.");
}
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please try again.");
scanner.nextLine(); // Clear input
}
} while (true);
}
private static void displayProducts() {
products.stream()
.sorted(Comparator.comparingInt(Product::getId))
.forEach(System.out::println);
}
private static void findHighestAndLowestPricedProducts() {
Optional<Product> highestPriceProduct = products.stream()
.max(Comparator.comparingDouble(Product::getPrice));
Optional<Product> lowestPriceProduct = products.stream()
.min(Comparator.comparingDouble(Product::getPrice));
System.out.println("Highest price product: " + highestPriceProduct.orElse(null));
System.out.println("Lowest price product: " + lowestPriceProduct.orElse(null));
}
private static void addProduct(Scanner scanner) {
int id;
String name;
String category;
double price;
do {
System.out.print("Enter product id: ");
id = scanner.nextInt();
scanner.nextLine(); // Consume new line character
} while (isProductIdExists(id));
System.out.print("Enter product name: ");
name = scanner.nextLine();
System.out.print("Enter product category: ");
category = scanner.nextLine();
System.out.print("Enter product price: ");
price = scanner.nextDouble();
Product product = new Product(id, name, category, price);
products.add(product);
System.out.println("Product added successfully.");
}
private static boolean isProductIdExists(int id) {
for (Product product : products) {
if (product.getId() == id) {
System.out.println("Product id already exists. Please enter a different id.");
return true;
}
}
return false;
}
private static void removeProduct(Scanner scanner) {
System.out.print("Enter product id to remove: ");
int id = scanner.nextInt();
Iterator<Product> iterator = products.iterator();
boolean found = false;
while (iterator.hasNext()) {
Product product = iterator.next();
if (product.getId() == id) {
iterator.remove();
found = true;
break;
}
}
if (found) {
System.out.println("Product removed successfully.");
} else {
System.out.println("Product not found.");
}
}
private static void filterTop3ExpensiveFoodProducts() {
products.stream()
.filter(p -> p.getCategory().equalsIgnoreCase("food"))
.sorted(Comparator.comparingDouble(Product::getPrice).reversed())
.limit(3)
.forEach(System.out::println);
}
}
注意事项：
Product需要实现Serializable接口，以支持序列化和反序列化。product.ser文件用于保存集合数据，如果product.ser文件不存在，之后的操作会创建这个文件。