我如何编辑程序以将变量分配给数组列表 [英] How do I edit my program in order to assign a variable to an array list

问题描述

所以我目前正在为一个学校项目工作.我的初始程序运行良好，然后被告知将数组重构为数组列表.

so I am currently working on a project for school. My initial program ran fine and then I was told to refactor my array into an array list.

Eclipse突出显示了一行特定的错误

Eclipse is highlighting one specific line with the error that

分配的左侧必须是变量" .

程序中的其他所有内容似乎都没有其他问题.

Everything else in the program seems to have no other issues.

我尝试了几种其他方法来解决此问题，并且碰壁了.我已经附上了导致我出现问题的代码部分的副本，希望这个问题不要太含糊.

I have tried a few different things to fix this problem and have hit a wall. I've attached a copy of the section of code causing me issue, and I hope this question isn't too vague.

import java.util.ArrayList;
import java.util.concurrent.ThreadLocalRandom;

public class StockPrices {

    static final int MAX_STOCK_COUNT = 24;
    static final int MIN_STOCK_PRICE = 10;
    static final int MAX_STOCK_PRICE = 100;

    // Create the array of Stock Objects
    ArrayList<Stock> myStocks = new ArrayList<Stock>();

    public StockPrices() {
        char startChar = 'A';
        String tmpSymbol = null;
        int startPrice = 0;
        int priceRightNow = 0;

        for (int idx = 0; idx < MAX_STOCK_COUNT; ++idx) {
            // Generate stock symbol for testing
            tmpSymbol = "" + (char) (startChar + idx) + (char) (startChar + idx + 1) + (char) (startChar + idx + 2);
            // Generate random data for pricing
            startPrice = ThreadLocalRandom.current().nextInt(MIN_STOCK_PRICE, MAX_STOCK_PRICE + 1);
            priceRightNow = ThreadLocalRandom.current().nextInt(MIN_STOCK_PRICE, MAX_STOCK_PRICE + 1);
            myStocks.get(idx) = new ArrayList <Stock>(tmpSymbol, startPrice, priceRightNow); //The issue is with this line starting with "myStocks"**
            System.out.println(myStocks.get(idx));
        }
    }
}

推荐答案

myStocks.get(idx)=新的ArrayList(tmpSymbol，startPrice，priceRightNow);

myStocks.get(idx) = new ArrayList (tmpSymbol, startPrice, priceRightNow);

此行代码从ArrayList中获取一个项目.没有设置.

This line of code is getting an item from your ArrayList. Not setting.

此外，即使它是 setting 而不是获取，您正在将ArrayList中的项目分配为另一个ArrayList ...，但您的ArrayList<>不是ArrayLists的ArrayList(跟随我)?它是一个ArrayList<股票>(股票清单).

Furthermore, even if it was setting instead of getting, you are assigning an item in your ArrayList to be another ArrayList... but your ArrayList<> is not an ArrayList of ArrayLists (follow me)? It is an ArrayList< Stock > (list of Stocks).

如果要添加新库存或更新，则需要执行以下操作:

If you want to add a new stock, or update, you need to do:

myStocks.add(new Stock(tmpSymbol, startPrice, priceRightNow); // add new

// OR

myStocks.set(idx, new Stock(tmpSymbol, startPrice, priceRightNow); // update at index

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