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这个简单的程序应该能够获得加价百分比和批发成本并计算零售价我在CALCULATE按钮上放置了一个动作侦听器，但是当我按下计算按钮时出现此错误：

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: 
For input string: "Enter the markup precentage" 
at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source) 
at java.lang.Double.parseDouble(Unknown Source) 
at mm$CalcListerner.actionPerformed(mm.java:58) 
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source) 
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) 
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) 
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)

有人可以帮我解决这个问题吗？

有人可以解释这些错误消息，因为我真的不明白吗？

我的代码是：

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

public class mm extends JFrame {

    private JTextField WholesaleCost;
    private JTextField markupPresentage;
    private JLabel WCost;
    private JLabel MPrecentage;
    private JButton button;
    private JPanel pannel;
    private final int Width = 250;
    private final int height = 320;

    public mm() {
        setTitle("Retail Price Calculator");
        setSize(Width, height);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        buildPanel();
        add(pannel);
    }

    private void buildPanel() {
        WholesaleCost = new JTextField(10);
        markupPresentage = new JTextField(10);

        WCost = new JLabel("enter the Whole Sale cost");
        MPrecentage = new JLabel("Enter the markup precentage");

        button = new JButton("Calculate");
        button.addActionListener(new CalcListerner());

        pannel = new JPanel();
        pannel.add(WholesaleCost);
        pannel.add(markupPresentage);
        pannel.add(WCost);
        pannel.add(MPrecentage);
        pannel.add(button);
    }

    private class CalcListerner implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            String WSaleinput;
            String MPres;
            WSaleinput = WholesaleCost.getText();
            MPres = MPrecentage.getText();

            double Value = Double.parseDouble(WSaleinput) * (Double.parseDouble(MPres) / 100);

            JOptionPane.showMessageDialog(null, "Retail Price is  " + Value);
        }
    }

    public static void main(String[] args) {
        mm x = new mm();
    }
}
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2 回答 2

3

您正在尝试将 MPrecentage.getText() 解析为双精度值，但这是标签的值，而不是输入的值。

你应该设置MPres为markupPercentage.getText();

如果 jvm 无法从您提供的字符串中获取数字，则会引发错误 NumberFormatException。在这种情况下，您试图从文本“输入标记百分比”中解析一个数字

于 2012-08-15T02:55:22.830 回答
3

您试图引用错误的组件。

这

WSaleinput=WholesaleCost.getText();
MPres =MPrecentage.getText();

实际上应该是

WSaleinput = WholesaleCost.getText();
MPres = markupPresentage.getText();
于 2012-08-15T02:56:18.460 回答