Java：将ArrayList与JComboBox和JTextField结合使用

Question

我目前正在尝试创建一个GUI，该GUI从包含汇率的.txt文件中获取信息。

文本文件包含3个不同的值，并用'，'分隔。

值是：货币名称，汇率，货币符号。

我正在运行程序，以便将这3个值存储到3个不同的ArrayLists中

该程序还将使用货币名称更新JComboBox。

但是，我现在需要该程序根据用户在JComboBox中选择的货币名称来选择正确的汇率和货币符号。

例如，如果用户选择USD（arrayCurrency）并将5输入到JTextField中，则程序需要选择正确的汇率（arrayRate）。

Answer 1

但是，我现在需要该程序根据用户在JComboBox中选择的货币名称来选择正确的汇率和货币符号。

这不完全是一个问题...我假设您要输入以下内容：

如何从JComboBox获取值？ -> yourJCBox.getSelectedItem();

现在有了该字符串-您需要确定如何将汇率映射到美元金额。 无论是2d，3d阵列还是您设计的对象：

public class myCurrency() {
  String currnecy;
  String symbol;
  Double rate;

  public myCurrency(String c, String s, Double r) {
    // Constructor stuff
  }

  // Getters and setters
}

现在，您有了所有需要检查的想法，以检查是否应显示某些汇率和符号的货币。

Answer 2

您可以通过以下方式轻松管理它：

1. 创建货币类（数据类型）
2. 将货币存储在Map而不是List

下面是示例代码：

import java.util.HashMap;
import java.util.Map;

class Currency {
    String code;
    double convertionRate;
    String symbol;

    Currency(String code, double convertionRate, String symbol) {
        this.code = code;
        this.convertionRate = convertionRate;
        this.symbol = symbol;
    }

    public double getConvertionRate() {
        return convertionRate;
    }

    public void setConvertionRate(double convertionRate) {
        this.convertionRate = convertionRate;
    }

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }
}

public class Main {
    public static void main(String[] args) {
        Map<String, Currency> currencyMap = new HashMap<String, Currency>();
        // Populate currencyMap with values read from the .txt file e.g.
        currencyMap.put("USD", new Currency("USD", 1.60, "$"));
        // Replace the above line with currencyMap.put(currency_code-from-file,new
        // Currency(currency_code-from-file,conversion_rate-from-file,currency_symbol-from-file));
        // and use it inside the loop which you must be using to read the content from .txt file

        // Getting the corresponding conversion rate and symbol for a currency e.g. USD
        Currency currency = currencyMap.get("USD");
        // Replace the above statement with Currency
        // currency=currencyMap.get(String.valueOf(JComboBox.getSelectedItem()) in your
        // program.
        double convertionRate = currency.getConvertionRate();
        String symbol = currency.getSymbol();
        // Use convertionRate and symbol in your calculation
    }
}

更新：由于您在评论中提到您难以将货币加载到currencyMap ，因此我添加了以下更新，只是为了演示如何将货币从.txt文件加载到currencyMap ：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

class Currency {
    String code;
    double convertionRate;
    String symbol;

    Currency(String code, double convertionRate, String symbol) {
        this.code = code;
        this.convertionRate = convertionRate;
        this.symbol = symbol;
    }

    public double getConvertionRate() {
        return convertionRate;
    }

    public void setConvertionRate(double convertionRate) {
        this.convertionRate = convertionRate;
    }

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }
}

public class Main {
    Map<String, Currency> currencyMap = new HashMap<String, Currency>();

    public static void main(String[] args) {
        Main main = new Main();
        main.populateCurrencyMap();

        // Getting the corresponding conversion rate and symbol for a currency e.g. USD
        Currency currency = main.currencyMap.get("USD");
        if (currency != null)
            System.out.println("Rate: " + currency.getConvertionRate() + ", Symbol: " + currency.getSymbol());
    }

    void populateCurrencyMap() {
        File file = new File(
                "/Users/arvind.avinash/Documents/workspace-spring-tool-suite-4-4.4.0.RELEASE/AdHoc/src/currency2.txt");
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(file), "UTF8"));

            String line = in.readLine().trim();

            while (line != null) {
                String[] parts = line.split(",");
                String currency = parts[0].trim();
                double rate = Double.parseDouble(parts[1].trim());
                String symbol = parts[2].trim();

                currencyMap.put(currency, new Currency(currency, rate, symbol));
                line = in.readLine();
            }

            in.close();

        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

输出：

Rate: 1.6, Symbol: $

currency2.txt的内容：

USD, 1.60, $
EUR, 1.41, €