Java 货币转换器 GUI答案

【问题标题】：Java Currency Converter GUIJava 货币转换器 GUI
【发布时间】：2013-04-28 06:19:17
【问题描述】：

我正在尝试制作一个简单的 java 货币转换器 GUI。到目前为止，我有这个：（4 部分）

如何设置 jcombbox 中每个项目的值（例如每种货币），以便我可以使用它们来计算转换？

这是第一部分（1 个组合框）：

import java.awt.*;
import java.awt.event.*; 
import javax.swing.*;
public class test extends JPanel
{
private JPanel panel;
private JLabel messageLabel;
private JTextField USDTextField;
private JPanel CurrencyPanel;         
private JComboBox CurrencyBox;       
private String[] Currency  = { "USD - United States Dollar",
                 "GBP - Great Britain Pound", "AUD - Australian Dollar",
                 "EUR- Euro"};
public currency1()
{
  setLayout(new BorderLayout(4,1));
  buildCurrencyPanel();
  add(CurrencyPanel, BorderLayout.CENTER);
  setVisible(true);
  setBorder(BorderFactory.createTitledBorder("Select currency"));

}
private void buildCurrencyPanel()
{
  CurrencyPanel = new JPanel();
  CurrencyBox = new JComboBox(Currency);
  CurrencyPanel.add(CurrencyBox);
}
 public static void main(String[] args)
{
   new currency1();
}
}

【问题讨论】：

我以为您已经制作了一个用于从代码中消除并发问题的 GUI，“Java 并发转换器”。

标签： java swing converter jcombobox currency

【解决方案1】：

也许尝试使用 Map（例如 HashMap）而不是数组？键是货币名称，值是货币的值。所以而不是：

private String[] Currency  = { "USD - United States Dollar",
                 "GBP - Great Britain Pound", "AUD - Australian Dollar",
                 "EUR- Euro"};

我会成功的：

private Map<String, Double> Currency = new HashMap<>();
//This is an initialization block
{
   Currency.put("USD - United States Dollar", 4.44);
   Currency.put("GBP - Great Britain Pound", 5.55);
   //and so on...
}

【讨论】：

【解决方案2】：

仅评论，我对货币转换器的看法

货币对的定义，默认有基础货币和可变货币
外汇汇率的定义
买卖定义
基/变量的定义
（将所有上午点放在一起）那么有四种可能的组合
- 购买基础（1,000 欧元。- 1.31）
- 卖出基数（1,000 欧元。- 1.31 时）
- 购买变量（1,000 美元。- 1.311）
- 卖出变量（1,000 美元。- 1.311）
GBP/USD 有反向计算方法

【讨论】：

【解决方案3】：

可能的解决方案的建议：

我将创建一个 Currency 类，该类具有一个 String currencyName 字段和一个双 currencyRate 字段，该字段与某个标准相比保持其汇率。
我会用 Currency 对象填充我的 JComboBox 模型。
我会给 JCOmboBox 一个单元格渲染器，以便它显示货币名称。
我会给我的 GUI 一个“转换”JButton
在该按钮的操作中，我会通过调用 getSelectedItem() 从两个组合框中提取选定的货币，并使用它们来计算答案。
在尝试计算之前，请确保所选项目都不为空。
或者这可以通过添加到两个组合框的 ActionListener 来完成，但是我首先必须确保所选值不为空或所选索引不为 -1。

【讨论】：

【解决方案4】：

创建一个包含双精度值的 Currency 类，该值是货币的值（您可以选择如何计算这些值）。

让货币的toString() 返回组合框中应显示的内容，例如“USD - 美国美元”。

现在确保您的JComboBox 使用泛型，因此当您调用getSelectedItem() 时，您不必将其转换为Currency，如new JComboBox<Currency>()。如果您的项目设置在 Java 6 上，您仍然可以使用 JComboBox 泛型，即使它是在 Java 7 中添加的，因为有一些称为类型擦除的奇特事物。查看详情。

【讨论】：

【解决方案5】：

我在点击您提供的 URL 时没有看到太多内容，所以我很确定这是否完全适合，但此类问题通常最好使用 Java enums 来解决。特别是，您可以使用类似以下的内容来存储您的转换字符串和汇率（请注意，我选择了任意转换率 - 用实际汇率代替这些）：

public enum Currency {
    USD(1.0,"United States Dollar"),
    GPB(0.9,"Great Britain Pound"),
    AUD(0.8,"Australian Dollar"),
    EUR(0.7,"Euro");

    private double conversionRatio;
    private String description;

    private Currency(double conversionRatio, String description) {
        this.conversionRatio = conversionRatio;
        this.description = description;
    }

    public double getConversionRatio() {
        return conversionRatio;
    }

    public String getDescription() {
        return description;
    }

    public void toString() {
            return new StringBuilder(name()).append(" - ").append(getDescription()).toString();
    }

}

然后您可以像这样将这些添加到您的组合框中：

for( Currency currency : Currency.values() ) {
     CurrencyBox.addItem(currency);
}

【讨论】：

您不想将转换率硬编码到枚举中，因为它们会波动并且会波动。最好创建一个没有转化率的枚举，然后也许使用 EnumMap 来保存与每个 Conversion 枚举项关联的速率。
我不一定同意这一点。这一切都取决于程序的规范。如果它是为了保持最新的转换率，那么我会同意你的看法。但是在看这个时，我并没有想到是这种情况，并选择提供静态解决方案。但为了清楚起见 - 让我们问一下......@user2348024，如果不重建项目（即在运行时从配置文件读取或通过 Web 服务检索等），转换率是否需要更改？
可能。我已经对你投了赞成票，因为我喜欢你使用枚举的一般建议。
感谢各位的帮助。我是 Java 新手，我不想使用所有这些东西，否则我的教授会认为我在复制/粘贴，因为我们还没有学会这一点。但是由于第一个回复说可以使用 ActionListener（我们有点熟悉）来完成，我想我会这样做。再次感谢

【解决方案6】：

package convert;

public class CConverter extends javax.swing.JFrame {

    // Currency Values {Rupee,Dollar,Pound,Yen,Euro} 
double curr1[] = {0,1,0.015,0.012,1.67,0.014};
double curr2[] = {0,1,0.015,0.012,1.67,0.014}; 

/**
 * Creates new form CConverter
 */
public CConverter() {
    initComponents();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jLabel1 = new javax.swing.JLabel();
    jcmbCurrency1 = new javax.swing.JComboBox<>();
    jcmbCurrency2 = new javax.swing.JComboBox<>();
    jtxtAmount = new javax.swing.JTextField();
    jlblConversion = new javax.swing.JLabel();
    jbtnConvert = new javax.swing.JButton();
    jbtnReset = new javax.swing.JButton();
    jtxtConversion = new javax.swing.JTextField();
    jbtnExit = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jLabel1.setFont(new java.awt.Font("Tahoma", 1, 18)); // NOI18N
    jLabel1.setText("Currency Converter");

    jcmbCurrency1.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Choose One", "INDIA Rupee", "US Dollar", "UK Pound", "JAPAN Yen", "Euro" }));

    jcmbCurrency2.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Choose Other", "INDIA Rupee", "US Dollar", "UK Pound", "JAPAN Yen", "Euro" }));

    jtxtAmount.setText("Amount");

    jlblConversion.setText("Conversion");

    jbtnConvert.setText("CONVERT");
    jbtnConvert.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jbtnConvertActionPerformed(evt);
        }
    });

    jbtnReset.setText("RESET");
    jbtnReset.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jbtnResetActionPerformed(evt);
        }
    });

    jtxtConversion.setFont(new java.awt.Font("Tahoma", 1, 14)); // NOI18N
    jtxtConversion.setForeground(new java.awt.Color(0, 0, 204));
    jtxtConversion.setText("Converted Value");

    jbtnExit.setText("Exit");
    jbtnExit.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jbtnExitActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(0, 0, Short.MAX_VALUE)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                .addComponent(jLabel1)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jbtnConvert)
                    .addGap(18, 18, 18)
                    .addComponent(jbtnReset, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addComponent(jcmbCurrency1, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jcmbCurrency2, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jtxtAmount)
                .addComponent(jlblConversion, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jtxtConversion))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        .addGroup(layout.createSequentialGroup()
            .addGap(158, 158, 158)
            .addComponent(jbtnExit)
            .addContainerGap(191, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(22, 22, 22)
            .addComponent(jLabel1)
            .addGap(28, 28, 28)
            .addComponent(jcmbCurrency1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jcmbCurrency2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jtxtAmount, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(38, 38, 38)
            .addComponent(jlblConversion)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jtxtConversion, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jbtnConvert)
                .addComponent(jbtnReset))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addComponent(jbtnExit)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void jbtnConvertActionPerformed(java.awt.event.ActionEvent evt) {                                            
    // TODO add your handling code here:


    double amt = Double.parseDouble(jtxtAmount.getText());

    int obj1 = jcmbCurrency1.getSelectedIndex();
    int obj2 = jcmbCurrency2.getSelectedIndex();

    if (obj1 == obj2){
        String samecur = "Both the currencies cannot be the same";
        jtxtConversion.setText(samecur);
    }
    else {
        double res = (amt/curr1[obj1])*curr2[obj2];

        String conv = String.format("%.2f",res);
        jtxtConversion.setText(conv);
    }

}                                           

private void jbtnResetActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
    jtxtAmount.setText(null);
    jtxtConversion.setText(null);
    jcmbCurrency1.setSelectedIndex(0);
    jcmbCurrency2.setSelectedIndex(0);
}                                         

private void jbtnExitActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // TODO add your handling code here:
    System.exit(0);
}                                        

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(CConverter.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(CConverter.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(CConverter.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(CConverter.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new CConverter().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JLabel jLabel1;
private javax.swing.JButton jbtnConvert;
private javax.swing.JButton jbtnExit;
private javax.swing.JButton jbtnReset;
private javax.swing.JComboBox<String> jcmbCurrency1;
private javax.swing.JComboBox<String> jcmbCurrency2;
private javax.swing.JLabel jlblConversion;
private javax.swing.JTextField jtxtAmount;
private javax.swing.JTextField jtxtConversion;
// End of variables declaration                   
}

试试这个代码我以印度卢比为基础它可以转换印度卢比美元英镑日圆欧元

【讨论】：

【解决方案7】：

基本上，我理解"Exchange rate" 的方式是，将一种货币兑换成另一种货币需要多少钱。

对我来说，这意味着需要将一种货币与另一种货币关联起来。这可以是“货币对”

除了前面的一些建议（例如，使用枚举）之外，作为蛮力，可以使用与汇率相关联的货币对进行转换。

例如（请注意，下面的代码将需要适当的验证和缩放/舍入）：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.math.BigDecimal;
import java.text.NumberFormat;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import static javax.swing.JFrame.EXIT_ON_CLOSE;

public class Main extends JPanel {
    enum Currency {
        USD("United States Dollar"),
        GBR("Great Britain Pound"),
        AUD("Australian Dollar"),
        EUR("Euro");

        private String description;

        Currency(String description) {
            this.description = description;
        }

        @Override public String toString() {
            return this.name() + " - " + this.description;
        }
    }

    class CurrencyPair {
        private final Currency from;
        private final Currency to;

        public CurrencyPair(Currency from, Currency to) {
            this.from = from;
            this.to = to;
        }

        @Override public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            CurrencyPair that = (CurrencyPair) o;
            if (from != that.from) return false;
            return to == that.to;
        }

        @Override public int hashCode() {
            int result = from.hashCode();
            result = 31 * result + to.hashCode();
            return result;
        }
    }

    private final Map<CurrencyPair, BigDecimal> exchangeRates = new HashMap<CurrencyPair, BigDecimal>() {{
        put(new CurrencyPair(Main.Currency.USD, Main.Currency.USD), BigDecimal.valueOf(1));
        put(new CurrencyPair(Main.Currency.AUD, Main.Currency.AUD), BigDecimal.valueOf(1));
        put(new CurrencyPair(Main.Currency.EUR, Main.Currency.EUR), BigDecimal.valueOf(1));
        put(new CurrencyPair(Main.Currency.GBR, Main.Currency.GBR), BigDecimal.valueOf(1));

        put(new CurrencyPair(Main.Currency.USD, Main.Currency.GBR), BigDecimal.valueOf(0.75));
        put(new CurrencyPair(Main.Currency.USD, Main.Currency.AUD), BigDecimal.valueOf(1.33));
        put(new CurrencyPair(Main.Currency.USD, Main.Currency.EUR), BigDecimal.valueOf(0.89));

        put(new CurrencyPair(Main.Currency.EUR, Main.Currency.USD), BigDecimal.valueOf(1.12));
        put(new CurrencyPair(Main.Currency.EUR, Main.Currency.AUD), BigDecimal.valueOf(1.49));
        put(new CurrencyPair(Main.Currency.EUR, Main.Currency.GBR), BigDecimal.valueOf(0.85));

        put(new CurrencyPair(Main.Currency.AUD, Main.Currency.USD), BigDecimal.valueOf(0.74));
        put(new CurrencyPair(Main.Currency.AUD, Main.Currency.EUR), BigDecimal.valueOf(0.67));
        put(new CurrencyPair(Main.Currency.AUD, Main.Currency.GBR), BigDecimal.valueOf(0.57));

        put(new CurrencyPair(Main.Currency.GBR, Main.Currency.USD), BigDecimal.valueOf(1.33));
        put(new CurrencyPair(Main.Currency.GBR, Main.Currency.EUR), BigDecimal.valueOf(1.18));
        put(new CurrencyPair(Main.Currency.GBR, Main.Currency.AUD), BigDecimal.valueOf(1.76));

    }};

    public Main() {
        super(new FlowLayout(FlowLayout.LEADING));

        // Amount
        JTextField amountInput = new JTextField(20);
        JPanel amount = new JPanel();
        amount.add(amountInput);
        amount.setBorder(BorderFactory.createTitledBorder("Enter Ammount"));
        add(amount, BorderLayout.CENTER);

        // From
        JPanel from = new JPanel();
        JComboBox fromOptions = new JComboBox(Currency.values());
        from.add(fromOptions);
        from.setBorder(BorderFactory.createTitledBorder("Select currency"));
        add(from, BorderLayout.CENTER);

        // To
        JComboBox toOptions = new JComboBox(Currency.values());
        JPanel to = new JPanel();
        to.add(toOptions);
        to.setBorder(BorderFactory.createTitledBorder("Convert to"));
        add(to, BorderLayout.CENTER);

        // Convert Action
        JLabel convertText = new JLabel();
        JButton convertCmd = new JButton("Convert");
        convertCmd.addActionListener(convertAction(amountInput, fromOptions, toOptions, convertText));
        JPanel convert = new JPanel();
        convert.add(convertCmd);
        convert.add(convertText);
        add(convert);
    }

    private ActionListener convertAction(
            final JTextField amountInput,
            final JComboBox fromOptions,
            final JComboBox toOptions,
            final JLabel convertText) {

        return new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                // TODO: Needs proper validation
                String amountInputText = amountInput.getText();
                if ("".equals(amountInputText)) { return; }

                // Convert
                BigDecimal conversion = convertCurrency(amountInputText);
                convertText.setText(NumberFormat
                        .getCurrencyInstance(Locale.US)
                        .format(conversion));
            }

            private BigDecimal convertCurrency(String amountInputText) {
                // TODO: Needs proper rounding and precision setting
                CurrencyPair currencyPair = new CurrencyPair(
                        (Currency) fromOptions.getSelectedItem(),
                        (Currency) toOptions.getSelectedItem());
                BigDecimal rate = exchangeRates.get(currencyPair);
                BigDecimal amount = new BigDecimal(amountInputText);
                return amount.multiply(rate);
            }
        };
    }


    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.getContentPane().add(new Main());
        frame.setTitle("Currency Thing");
        frame.setSize(500, 500);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }


}

【讨论】：