Question

代码是使用FIFO和LIFO来模拟销售库存。我现在只想让FIFO工作，我们正在使用策略模式。我和我的朋友相信我们的代码是正确的，因为没有错误，不管你运行代码。下面我有我的所有课程（标记为1-5，以及输出（标记为输出））

第1类

package cop4814;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.*;

public class Portfolio {
private SellStrategy strategy;
List<Transaction> buyList = new ArrayList<>();
List<Transaction> sellList = new ArrayList<>();

public boolean readDataFile(String path) {
    try {
        Scanner in = new Scanner(new File(path));
        while (in.hasNextLine()) {
            String[] fields = in.nextLine().split(",");
            if (fields[0].equals("B")) {
                buyList.add(new Transaction(fields));
            } else if (fields[0].equals("S")) {
                sellList.add(new Transaction(fields));
            }

        }
    } catch (FileNotFoundException ex) {
        System.out.println("Error: " + ex.toString());
        return false;
    }
    return true;
}

public void processTransactions() {
    for (Transaction t : sellList) {
        System.out.println(strategy.sell(t,buyList));
    }
}

public void setSellStrategy(SellStrategy howToSell) {
    strategy = howToSell;
}

}

第2类

package cop4814;

import java.util.List;

public interface SellStrategy 
{
   public String sell(Transaction stockToSell, List<Transaction> buyList);

}

第3类

package cop4814;

import java.util.List;

public class Sell_FIFO implements SellStrategy {

public String sell(Transaction stockToSell, List<Transaction> buyList) {
    //Find first occurrence of stockToSell
    Transaction found = buyList.get(buyList.indexOf(stockToSell));
    //Find difference between stockToSell and the first occurrence's shares
    int diff = stockToSell.numShares - found.numShares;

    //Loop to continue finding and remove stocks or shares as needed when the difference is greater than 0
    while (diff > 0){
            //remove from buy list
            buyList.remove(stockToSell);
            //find next stock to sell and find new diff
            found = buyList.get(buyList.indexOf(stockToSell));
            diff = stockToSell.numShares - found.numShares;

    }

    //Loop has stopped because diff is now 0 or LT 0
    if (diff == 0) {
        //remove stock
        buyList.remove(stockToSell);
    } else {
        found.numShares = found.numShares - diff;
    }

    return "";
}

}

第4类（有我的变量）

    package cop4814;

    public class Transaction {
    String action; // s or s
    String ticker;
    String datepurchased;
    int numShares;
    double purchPrice;

    public Transaction(String[] fields) {
        action = fields[0];
        datepurchased = fields[1];
        numShares = Integer.parseInt(fields[2]);
        purchPrice = Double.parseDouble(fields[3]);
        ticker = fields[4];

    }

    public boolean equals(Transaction o) {
        return this.ticker.equals(o.ticker);
    }

    }

第5课（我的考试类）

import cop4814.*;

public class PortfolioTester {

    private static final String inputFilePath = "transactions.txt";

    void start() {
        Portfolio p = new Portfolio();
        if( p.readDataFile( inputFilePath )) {
            p.setSellStrategy( new Sell_LIFO() );
            p.processTransactions();      // also prints the report
            p.setSellStrategy( new Sell_FIFO() );
            p.processTransactions();      // prints a second report
        }
        else {
            System.out.println("Unable to open input file: " + inputFilePath );
        }           
    }

    public static void main(String[] args) {
        new PortfolioTester().start();
    }

}

输出

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
    at java.util.ArrayList.elementData(ArrayList.java:418)
    at java.util.ArrayList.get(ArrayList.java:431)
    at cop4814.Sell_FIFO.sell(Sell_FIFO.java:18)
    at cop4814.Portfolio.processTransactions(Portfolio.java:43)
    at PortfolioTester.start(PortfolioTester.java:13)
    at PortfolioTester.main(PortfolioTester.java:21)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

Answer 1

您收到ArrayIndexOutOfBoundsException，这意味着您已尝试访问具有非法索引的数组。

错误可能来自这一行：

Transaction found = buyList.get(buyList.indexOf(stockToSell));

您应首先检查列表中是否存在该项：

if (buyList.contains(stockToSell)) {
    // do work
}

代码不会编译，没有可见的错误

1 个答案: