java - arrayList 存储了 2 个以上的对象，如果用户搜索它们如何获得返回

Question

因此，在该程序中，用户在一个文件 Inv.java 中输入对象的数据，然后该信息存储在 Product.java 和 store.java 中。从 store.java 有一个 arrayList 保存信息，但是当尝试放入 2 个项目时，第二个对象会覆盖第一个对象，我该如何解决这个问题以及如何能够在 Inv 中调用对象。 java

Inv.java 代码

import java.util.Scanner;
import java.util.*;
import java.util.ArrayList;

public class Inv
{


public static void main(String args[])
{

    Scanner console = new Scanner(System.in);

    String str;
    char c;
    int n=0;




    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)// Exits the program when 4 is pressed
    {
        System.out.print("\n Please enter option 1-4 to continue...: ");
        n = Integer.parseInt(System.console().readLine());
        // Reads user input and takes them to selected code.
        if (n>4||n<1)
        {
            System.out.print("Invalid input, please try again...");
            continue;
        }
        if (n==1)// Takes to option 1 or addItem()
        {
            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)// Takes to option 2 or prodData
        {
            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)// Takes to option 3 or replenStrat
        {
            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");

}
// Global variables so that any class can call it and use the information in it
public static Product product;
public static Store store;
// Where the user inputs the data for the item
public static void addItem ()
{
    Scanner console = new Scanner(System.in);
    product = new Product();// initiates the product and store to being empty.
    store = new Store();

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


        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");
        // stores the item in the array
        store.add(product);


}
// Where the product information is being returned to the user
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();//

    product = store.getProduct(pOption); //Checks to see if the item is created
                                        // so that data can be displayed
    if (product != null){
        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());
    }else{
        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();
    }
}

}

Product.java 代码

public class Product
{
    public String name;
    public double price, sUpPrice, unitCost, invCost;
    public int stock, demand;


    public Product()
    {
        name = "";
        price = 0;
        sUpPrice = 0;
        unitCost = 0;
        invCost = 0;
        stock = 0;
        demand = 0;

    }

        public void setName(String name) {
            this.name = name;
        }
        public String getName() {
            return this.name;
        }

        public void setPrice(double price) {
            this.price = price;
        }
        public double getPrice() {
            return this.price;
        }   
        public void setsUpPrice(double sUpPrice) {
            this.sUpPrice = sUpPrice;
        }
        public double getsUpPrice() {
            return this.sUpPrice;
        }   
        public void setunitCost(double unitCost) {
            this.unitCost = unitCost;
        }
        public double getunitCost() {
            return this.unitCost;
        }   
        public void setinvCost(double invCost) {
            this.invCost = invCost;
        }
        public double getinvCost() {
            return this.invCost;
        }
        public void setstock(int stock) {
            this.stock = stock;
        }
        public int getstock() {
            return this.stock;
        }
        public void setdRate(int demand) {
            this.demand = demand;
        }
        public int getdRate() {
            return this.demand;
        }

}

store.java 代码

import java.util.*;
import java.util.ArrayList;

public class Store{
public ArrayList <Product> ProductList = new ArrayList<Product> ();

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

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

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;
 }

}

如有任何帮助，我们将不胜感激。

Answer 1

问题出在 Inv.addItem() 方法中，每次调用它时都会实例化变量 store 。

store = new Store();

查看您的代码，您应该在 Inv 中实例化它:

public static Store store = new Store();