Question

我一直在尝试从文本字段中获取输入并将其放在Double变量中。但是，当我尝试使用Double.parseDouble(textTF.getText())我得到错误时，我使用扫描仪测试它工作正常

private class NumRTFHandler implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        String romanN = "";
        String dec = numDTF.getText();
        Double decimal = Double.parseDouble(dec);
    }
}

我猜这可能是动作听众，但我不知道如何处理它。 Double.parseDouble()既不适用于textField也不适用于字符串。

请帮助。

这些是错误。

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)
at java.lang.Double.parseDouble(Unknown Source)
at RomanNumeralConvertert$NumRTFHandler.actionPerformed(RomanNumeralConvertert.java:40)
at javax.swing.JTextField.fireActionPerformed(Unknown Source)
at javax.swing.JTextField.postActionEvent(Unknown Source)
at javax.swing.JTextField$NotifyAction.actionPerformed(Unknown Source)
at javax.swing.SwingUtilities.notifyAction(Unknown Source)
at javax.swing.JComponent.processKeyBinding(Unknown Source)
at javax.swing.JComponent.processKeyBindings(Unknown Source)
at javax.swing.JComponent.processKeyEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

我在顶部声明了numDTF

JTextField numDTF;

并获得用户的输入。

编辑：

这是整个代码

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class RomanNumeralConvertert extends JFrame {

  private static final int HEIGHT = 60;  
  private static final int WIDTH = 600;

  private JLabel numRL, numDL;  
  private JTextField numRTF, numDTF;
  private NumRTFHandler nrh;
  private NumDTFHandler ndh;

  public RomanNumeralConvertert() {
    setTitle("Roman Numeral to Decimal Converter");                  
    numRL = new JLabel("Decimal Value: ", SwingConstants.RIGHT);
    numDL = new JLabel("Roman Numeral: ", SwingConstants.RIGHT);
    numRTF = new JTextField(10);
    numDTF = new JTextField(10);
    nrh = new NumRTFHandler();
    ndh = new NumDTFHandler();
    numRTF.addActionListener(nrh);
    numDTF.addActionListener(ndh);

    Container pane = getContentPane();            
    pane.setLayout(new GridLayout(1, 4));
    pane.add(numDL); pane.add(numDTF);
    pane.add(numRL); pane.add(numRTF);

    setSize(WIDTH, HEIGHT);                     
    setVisible(true);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
  }

  private class NumRTFHandler implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      String romanN = "";
      String dec = numDTF.getText();
      Double decimal = Double.parseDouble(dec);
      //converting to Roman Numerals 
      while(decimal >= 1000){
        romanN += "M";
        decimal -= 1000.0;  
      }
      while(decimal >= 900){
        romanN += "CM";
        decimal -= 900;  
      }
      while(decimal >= 500){
        romanN += "D";
        decimal -= 500;  
      }
      while(decimal >= 400){
        romanN += "CD";
        decimal -= 400;  
      }
      while(decimal >= 100){
        romanN += "C";
        decimal -= 100;  
      }
      while(decimal >= 90){
        romanN += "XC";
        decimal -= 90;  
      }
      while(decimal >= 50){
        romanN += "L";
        decimal -= 50;  
      }
      while(decimal >= 40){
        romanN += "XL";
        decimal -= 40;  
      }
      while(decimal >= 10){
        romanN += "X";
        decimal -= 10;  
      }
      while(decimal >= 9){
        romanN += "IX";
        decimal -= 9;  
      }
      while(decimal >= 5){
        romanN += "V";
        decimal -= 5;  
      }
      while(decimal >= 4){
        romanN += "IV";
        decimal -= 4;  
      }
      while(decimal >= 1){
        romanN += "I";
        decimal -= 1;  
      }
      numRTF.setText(romanN);
    }
  }

  private class NumDTFHandler implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      String romanN = numDTF.getText();
      double decimal = 0;
      romanN.toUpperCase();
      int i=0;
      while(i <= romanN.length()){
        char char1 = romanN.charAt(i);
        i++;
        char char2 ='i';
        if(i < romanN.length()){
          char2 = romanN.charAt(i+1);
          i++;
        }
        if( char1 == ('M')){
          decimal +=1000;
        }
        if( char1 == ('D')){
          decimal +=500;
        }
        if( char1 ==('C')){
          if( char2 == ('M')){
            decimal +=900;
          }
          if( char1 == ('D')){
            decimal +=400;
          }
        }else{
          decimal += 100;
        }
        if( char1 == ('L')){
          decimal +=50;
        }
        if( char1 == ('X')){
          if( char2 == ('C')){
            decimal +=90;
          }
          if( char1 == ('L')){
            decimal +=40;
          }
        }else{
          decimal += 10;
        }
        if( char1 == ('V')){
          decimal +=5;
        }
        if( char1 == ('1')){
          if( char2 == ('X')){
            decimal +=9;
          }
          if( char1 == ('V')){
            decimal +=4;
          }
       }else{
          decimal += 1;
       }
      }
      numDTF.setText("" + decimal);

    }
  }

  public static void main(String[] args) {
    RomanNumeralConvertert gui = new RomanNumeralConvertert();
  }
  // End of the Code
}

我无法理解，我检查了逻辑并且没有问题。

编辑：

我已经解决了导致空字符串的问题。有一些文本字段名称切换到一起，只需更改名称，它现在正在工作，这里的逻辑几乎没有问题，但也解决了。

Answer 1

您收到empty string错误，并且从您发布的代码中我猜测调用getText()方法无法返回任何内容，因为numDTF没有值。

从文本字段使用Double.parseDouble时出错

1 个答案: