从不同文件添加项目并使用数组列表将它们存储在另一个文件中

Posted 2023-02-26

【中文标题】从不同文件添加项目并使用数组列表将它们存储在另一个文件中

【英文标题】：Adding items from a different file and storing them in another using an array list

【发布时间】：2016-08-14 02:31:22

【问题描述】：

嘿，所以对于这个程序，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;

公共课 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());

第二个程序是带有数组列表的位，我似乎无法声明数组列表，也无法获取数据来填充数组列表。

公共类商店 私有 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。

【参考方案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) 行中，不要使用==，而是使用equals 方法进行比较。它将比较字符串的值。如果您使用==，它将比较两个字符串的对象引用，在您的情况下，即使它的值相同，它也会始终给出 false，因为您用于比较的两个字符串对象不同。

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

【讨论】：

好的，感谢我更新了代码，但现在它返回找不到符号的错误。符号：方法长度

它到底在哪里给出错误？没有正确的日志就不可能提供帮助

位置：ArrayList

类型的变量 ProductList

请查找更新后的代码，对于 List 没有像数组这样的长度属性。您必须使用 size() 方法来获取列表中的元素数。

导入 java.util.*;导入 java.util.ArrayList； public class Store 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

【参考方案2】：

在声明一个ArrayList时，需要指定它持有的数据类型。

在您的示例中，据我所知，productList 应该使用 private ArrayList<Product> productList = new ArrayList<>(); 进行实例化