java - 添加来自不同文件的项目并使用数组列表将它们存储在另一个文件中

Question

嘿，对于这个程序，我总共有 3 个文件，我想要实现的是从一个文件中获取用户输入的内容，然后将其存储在另一个文件的数组中，这样我就可以调用稍后再回来。

第一个程序是用户输入的位。

import java.util.Scanner;

导入java.util.*；导入 java.util.ArrayList;

公开课Inv{

public static void main(String args[])
{

    Scanner console = new Scanner(System.in);

    String str;
    char c;
    int n=0;


    //Product product  = new Product();


    System.out.println("        INVENTORY MANAGEMENT SYSTEM");
    System.out.println("===============================================");
    System.out.println("1. ADD PRODUCT DATA");
    System.out.println("2. VIEW PRODUCT DATA");
    System.out.println("3. VIEW REPRLENISHMENT STRATEGY");
    System.out.println("===============================================");
    System.out.println("4. EXIT PROGRAM");

    while(n!=4)
    {
        System.out.print("\n Please enter option 1-4 to continue...: ");
        n = Integer.parseInt(System.console().readLine());

        if (n>4||n<1)
        {
            System.out.print("Invalid input, please try again...");
            continue;
        }
        if (n==1)
        {
            str="y";
            while(str.equals("y")||str.equals("Y"))
            {

                Inv.addItem();
                System.out.print("Would you like to enter another product ? (Y or N) : ");
                str = console.next();
            }   
            continue;
        }
        if (n==2)
        {
            str="y";
            while(str.equals("y")||str.equals("Y"))
            {
                Inv.prodData();
                System.out.println("\n***************************************************\n");
                System.out.print("Stay viewing this page? (Y or N) ");
                str = console.next();

            }
            continue;
        }
        else

        if (n==3)
        {
            System.out.print("View Replenishment Strategy.");
            continue;
        }
    }
    System.out.print("\nThank you for using this inventory management software.\n");
    System.out.print("Developed by Xavier Edwards");
    System.out.println("\n***************************************************\n");

}

public static Product product;
public static Store store;
public static void addItem ()
{
    Scanner console = new Scanner(System.in);
    product = new Product();


    String desc, id, str="";
    double price = 0, sUpPrice = 0, unitCost = 0, inventoryCost = 0;
    int stock = 0, demand = 0;

    if (product == null) //If product 1 is empty
    {
        System.out.print("Please enter product description between 3 to 10 characters...: ");
        desc = console.next();
        desc = desc.toLowerCase();
        product.setName(desc);

        if ((desc.length() < 3 || desc.length() > 10))
        {
            System.out.println("\nThis Input is incorrect. Please make description between 3 to 10 characters.\n");
            System.out.println("Try again with different input. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.print("Please enter price in $ : ");
        price = console.nextDouble();
        product.setPrice(price);

        if (price < 0)
        {
            System.out.println("\nThis Input is incorrect. Please make sure attributes are positve numbers\n");
            System.out.println("Because of incorrect input, program will restart. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.print("Please enter set up price. $ : ");
        sUpPrice = console.nextDouble();
        product.setsUpPrice(sUpPrice);

        if (sUpPrice < 0)
        {
            System.out.println("\nThis Input is incorrect. Please make sure attributes are positve numbers\n");
            System.out.println("Because of incorrect input, program will restart. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.print("Please enter unit- cost. $ : ");
        unitCost = console.nextDouble();
        product.setunitCost(unitCost);

        if (unitCost < 0)
        {
            System.out.println("\nThis Input is incorrect. Please make sure attributes are positve numbers\n");
            System.out.println("Because of incorrect input, program will restart. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.print("Please enter the inventory cost. $ : ");
        inventoryCost = console.nextDouble();
        product.setinvCost(inventoryCost);

        if (inventoryCost < 0)
        {
            System.out.println("\nThis Input is incorrect. Please make sure attributes are positve numbers\n");
            System.out.println("Because of incorrect input, program will restart. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.print("Please enter the amount in stock : ");
        stock = console.nextInt();
        product.setstock(stock);

        if (stock < 0)
        {
            System.out.println("\nThis Input is incorrect. Please make sure attributes are positve numbers\n");
            System.out.println("Because of incorrect input, program will restart. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.print("Please enter the demand of the product : ");
        demand = console.nextInt();
        product.setdRate(demand);

        if (demand < 0)
        {
            System.out.println("\nThis Input is incorrect. Please make sure attributes are positve numbers\n");
            System.out.println("Because of incorrect input, program will restart. ");
            System.out.println("\n*****************************************\n");
            Inv.addItem();
        }

        System.out.println("\n*****************************************\n");
        System.out.print(desc +" Product was added successfully ");
        System.out.println("\n*****************************************\n");
        store.add(product); 

    }
}

public static void prodData()
{
    Scanner console = new Scanner(System.in);
    String pOption, str;

    System.out.print("\nEnter product description to view the data...\n");
    pOption = console.next();

    if (product == null)
    {
        System.out.println("\nThere is no information on this product.\n");

        System.out.println("\nWould you like to try again? (Y or N) \n");
        str = console.next();
        Inv.prodData();
    }

    System.out.println("The information for the product is..... ");
    System.out.println("\n*****************************************\n");
    System.out.println("Product description : "+product.getName());
    System.out.println("Price : $ "+product.getPrice());
    System.out.println("Set-up Price : $ "+product.getsUpPrice());
    System.out.println("Unit Cost : $ "+product.getunitCost());
    System.out.println("Inventory Cost : $ "+product.getinvCost());
    System.out.println("Amount of Stock : "+product.getstock());
    System.out.println("Amount of Stock : "+product.getdRate());

}

第二个程序是数组列表的位，我似乎无法声明数组列表，也无法获取填充数组列表的数据。

公共(public)类商店{ private ArrayList ProductList = new ArrayList();

public Store()
{
    //ArrayList = "";
}

public void add(Product product)
{           
    ProductList.add(product);
}

public Product getProduct(String prodName){
    for(int i = 0; i< ProductList.length; i++){
        if(ProductList(i).name == prodName){
            return ProductList(i);
        }
    }
}

任何帮助都会很棒，谢谢。

Answer 1

在 ArrayList 中，您需要使用要访问的对象的索引调用 get 方法。代替 getProduct 方法中的 ProductList(i)，执行 ProductList.get(i)

getProduct 函数现在应该如下所示:

public Product getProduct(String prodName) {
for (int i = 0; i < ProductList.size(); i++) {
if (ProductList.get(i).getName().equals(prodName)) {
return ProductList.get(i);
}
}
return null;
}

在ProductList.get(i).getName().equals(prodName)行而不是使用 == , 使用 equals比较的方法。它将比较字符串的值。如果你使用 == ，它将比较两个字符串的对象引用，在您的情况下，即使其值相同，它也始终会给出 false，因为您用于比较的两个字符串对象都不同。

也只是一个建议，在产品类中创建公共(public) getter setter 并通过 getName() 方法访问名称变量。