Question

我正在开发一个简单的POS程序。我有几个循环将零件信息添加到列表（invoiceList），然后在另一个列表（invoiceListMain）下订购所有零件，然后将所有发票订购到主列表（invoiceLogList）。所以基本上我在列表中的列表中有列表。

当我在print语句中输出整个列表时，这是有效的。但我需要能够解压缩列表。

[[738，[113,5.0,43.45]，[248,2.0,12.78]]，[459，[248,10.0,63.9]，[113,1.0,8.69]]

我收到此错误

ArrayListDemo.java:136：错误：不兼容的类型：String不能转换为ArrayList for（ArrayList line：invoiceLogList）

当我这样做时：

for(int i=0; i < invoiceLogList.size(); i++)
         {
           for(ArrayList<String> line : invoiceLogList)
           {
              System.out.print(" \n" + line.get(0));
           }

         }

在负面评级之前，请留下理由。

从研究开始，我认为这与我如何在列表中的列表中编译所有列表有关。

invoiceLogList.add(invoiceListMain.toString());

我必须添加.toString（）才能使其正常工作。所以我的猜测是我不能将它作为一个数组解压缩，因为它不再是一个数组？这是一个清单？我不是百分百肯定。

有没有人有更好的方法或如何解压缩数据的建议？

import java.util.ArrayList;
import java.util.Scanner;
import java.util.Random;


public class ArrayListDemo {

   public static void main(String[]args){

      //Part 1
      ArrayList<String> part1 = new ArrayList<String>();

      part1.add("06011");     
      part1.add("Castrol EDGE 0W20 Motor Oil - 1 qt");
      part1.add("9.49");

      //Part 2
      ArrayList<String> part2 = new ArrayList<String>();

      part2.add("248");     
      part2.add("Castrol EDGE 5W30 Motor Oil - 1 qt");
      part2.add("6.39");

      //Part 3   
      ArrayList<String> part3 = new ArrayList<String>();

      part3.add("03050");
      part3.add("Castrol Hypuron 10W30 Motor Oil - 1 gal");
      part3.add("6.39");

      //Part 4
      ArrayList<String> part4 = new ArrayList<String>();

      part4.add("113");
      part4.add("Castrol Pyroplex Protection ES Multi-Purpose Grease - 14 oz");
      part4.add("8.69");

      //Part 5
      ArrayList<String> part5 = new ArrayList<String>();

      part5.add("020");
      part5.add("Castrol GTZ ULTRACLEAN 5W20 Motor Oil - 6 gal");
      part5.add("69.99");


      //adding parts to main Part List
      ArrayList<ArrayList<String>> mainPartList = new ArrayList<ArrayList<String>>();

      mainPartList.add(part1);     
      mainPartList.add(part2);
      mainPartList.add(part3);
      mainPartList.add(part4);
      mainPartList.add(part5);


//-----INVOICE INPUT----------------------------------------------------------------------------

      //create a new scanner
      Scanner input = new Scanner(System.in);

      //Invoice Input
      String a = "";
      String invoiceNumber = "";
      String p = "";
      double q = 0.0;
      double partPrice = 0.0;
      double partSum = 0.0;
      String partNum = "";
      String partDescrip = "";
      String c = "";

      //Invoice Array

      ArrayList<String> invoiceLogList = new ArrayList<>();//Stores all invoices created
         do{//loop to create invoice

            ArrayList<String> invoiceListMain = new ArrayList<>();//stores individual invoices

            Random generator = new Random();//creates random invoice number     
            int sequence = generator.nextInt(1000);
            invoiceListMain.add(String.format("%03d", sequence));//invoice number
            System.out.print("Invoice #: " + sequence);

            do{//loop to add parts to invoice

               ArrayList<String> invoiceList = new ArrayList<String>();//stores part#, qty, sumTotal

               System.out.print("\n\nPart Number: ");
               p = input.next();

               //fetch part info from array mainPartList
               for(ArrayList<String> part : mainPartList)
               {
                  if(part.contains(p))
                  { 
                    for (int i = 0; i < 1; i++)
                       partNum = part.get(0);   
                       partDescrip = part.get(1);
                       invoiceList.add(partNum);//add part# to list
                       System.out.print("\t" + partNum + " - " + partDescrip);
                       partPrice = Double.parseDouble(part.get(2));//grabs price of part in list                   
                  }
               }

               System.out.print("\nQuantity: ");
               q = input.nextDouble(); //asks quantity sold
               invoiceList.add(Double.toString(q));//add quantity to list

               partSum = partPrice * q;
               invoiceList.add(Double.toString(partSum));//add part sum to list
               System.out.printf("\t $%.2f",partSum);

               System.out.print("\n\n---Add to cart?: ");
               c = input.next();

               invoiceListMain.add(invoiceList.toString());//adding part order to mainList

               }while(c.equalsIgnoreCase("Y")); 


             //Create Invoice Loop
             System.out.print("\n\nCreate a new Invoice? ");
             a = input.next();

             invoiceLogList.add(invoiceListMain.toString());

             }while(a.equalsIgnoreCase("Y"));



          //Print all invoices
          for(int i=0; i < invoiceLogList.size(); i++)
          {
            for(ArrayList<String> line : invoiceLogList)
            {
              System.out.print(" \n" + line.get(0));
            }

          }
   }
}

Answer 1

我尝试那个例子，那就是我得到的东西也许就是你想要的东西！

ArrayList<ArrayList<ArrayList<String>>> invoiceLogList= new ArrayList<ArrayList<ArrayList<String>>> ();
    ArrayList<ArrayList<String>> invoiceListMain= new ArrayList<ArrayList<String>>();
    ArrayList<String> c = new ArrayList<String>();
    c.add("13");
    c.add("50");
    c.add("43.45");
ArrayList<String> d = new ArrayList<String>();
d.add("728");
invoiceListMain.add(d);
invoiceListMain.add(c);
invoiceLogList.add(invoiceListMain);

  for(int i=0; i < invoiceLogList.size(); i++)
         {
           for(ArrayList<ArrayList<String>> line :invoiceLogList)
           {
              System.out.print(" \n" + line.get(0));
           }

         }

输出：

[728]
BUILD SUCCESSFUL (total time: 0 seconds)

Answer 2

这是因为您在两个循环标题中访问相同的列表，我相信进行此更正应该可以解决问题：

for(int i=0; i < invoiceLogList.size(); i++)
         {
           for(ArrayList<String> line : invoiceLogList.get(i))
           {
              System.out.print(" \n" + line.get(0));
           }

         }

Answer 3

如果你看看你的打印件，
你可以看到738和459是一个太高的水平。

以下是深度分解：
列表有2个元素
第1个包含3个元素的列表：
*一根绳子738
*一个字符串列表[113,5.0,43.45]
*一系列字符串[248,2.0,12.78]

这被认为是一个列表清单（来自你的故事）这是异常告诉你的。

添加到单独的ArrayLists到主ArrayList

3 个答案: