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我刚刚读完“Java for Dummies”并开始创建一个简单的 POS 程序。我一直无法让程序做我想做的事！我有两个 actionListener 链接到以下每个按钮，“Amigos”和“Fosters”。我还有两个文本字段，一个显示单个饮料的价格，另一个用于小计。我确实有小计工作将相同饮料的倍数加起来，但不是“朋友”和“福斯特”。这是通过尝试共享一个小计变量来编程的。我试图通过读取和写入单个文本文件来解决我的业余 Java 编程问题，但这对我来说也很困难！下面是我试图实现我的读写工作的代码。

这是我的第一个 Java 程序，所以请原谅我弄错了格式、标点符号和 Java 约定。也请原谅我缺乏评论。任何意见是极大的赞赏！

问候

路易斯

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.text.NumberFormat;
import java.io.FileNotFoundException;

class till_v2 {

    public static void main(String args[]) {

        JFrame frame;
        Container content_pane;
        JTextField textField, subTotal;
        JButton b1Amigos, b2Fosters;
        FlowLayout layout;

        frame = new JFrame();
        frame.setTitle("Louis' Till");

        content_pane = frame.getContentPane();

        textField = new JTextField("Price displayed here.",15);
        subTotal = new JTextField("Sub-Total.", 5);

        b1Amigos = new JButton("Amigos");
        b1Amigos.addActionListener(new AmigosAL(textField));
        b1Amigos.addActionListener(new subTotalAmigosUD(subTotal));

        b2Fosters = new JButton("Fosters");
        b2Fosters.addActionListener(new FostersAL(textField));
        b2Fosters.addActionListener(new subTotalFostersUD(subTotal));

        content_pane.add(textField);
        content_pane.add(subTotal);
        content_pane.add(b1Amigos);
        content_pane.add(b2Fosters);
        layout = new FlowLayout();
        content_pane.setLayout(layout);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);

    }
}

class subTotalFostersUD implements ActionListener {

    JTextField subTotal;
    int itemPrice;
    double sub_total;
    SUBTOTAL SUBTOTALobject = new SUBTOTAL();

    subTotalFostersUD(JTextField subTotal) {
        this.subTotal = subTotal;
    }
    //The problem could be here!
    public void actionPerformed(ActionEvent e) {
        try {
            itemPrice = 320;
            sub_total = SUBTOTALobject.SUBTOTAL(itemPrice);
            subTotal.setText("£"+sub_total);
        }

        catch (FileNotFoundException err) {
            System.out.println("1!");
        }
    }
}

class subTotalAmigosUD implements ActionListener {

    JTextField subTotal;
    int itemPrice;
    double sub_total;
    SUBTOTAL SUBTOTALobject = new SUBTOTAL();

    subTotalAmigosUD(JTextField subTotal) {
        this.subTotal = subTotal;
    }
    //Same problem as above!
    public void actionPerformed(ActionEvent e) {
        try {
            itemPrice = 330;
            sub_total = SUBTOTALobject.SUBTOTAL(itemPrice);
            subTotal.setText("£"+sub_total);
        }

        catch (FileNotFoundException err) {
            System.out.println("2!");
        }
    }
}

class AmigosAL implements ActionListener {

    JTextField textField;

    AmigosAL(JTextField textField) {
        this.textField = textField;
    }

    public void actionPerformed(ActionEvent e) {
        textField.setText("£3.30");
    }
}


class FostersAL implements ActionListener {

    JTextField textField;

    FostersAL(JTextField textField) {
        this.textField = textField;
    }

    public void actionPerformed(ActionEvent e) {
        textField.setText("£3.20");
    }
}

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

//The problem could be here!
public class SUBTOTAL {
    BufferedReader in;
    BufferedWriter out;
    int pennies;
    int itemPrice;
    public double sub_total;        

    public double SUBTOTAL(int itemPrice) throws FileNotFoundException {
        try {
            in = new BufferedReader(new FileReader("sub_total.txt"));
            pennies = Integer.parseInt(in.readLine());
            pennies = pennies + itemPrice;
            in.close();
        }

        catch(IOException e) {
            System.out.println("3!");
        }

        try {
            out = new BufferedWriter(new FileWriter("sub_total.txt"));
            out.write(pennies);
            out.close();
        }

        catch(IOException e){
            System.out.println("4!");
        }

        sub_total = pennies;
        sub_total = sub_total / 100;
        return sub_total;   
    }
}
4

2 回答 2

3

您收到此错误是因为您缺少文件sub_total.txt

使用所需内容创建此文件。在您拥有 .class 文件的同一文件夹中。

于 2011-02-20T17:05:55.807 回答
1

正如 Vivek 所说，它应该可以解决您的问题。

但是你会得到NumberFormatException

out.write(pennies);以指定要写入的字符int的数据类型写入文件。

但是小计可以超过一个字符，（小计随着项目数量的增加而增加）。

当小计超过一个字符时，它会在文本文件中写入垃圾值sub_total.txt

Integer.parseInt(in.readLine());尝试读取数据并将其String解析为int

结果是NumberFormatException

解决方案：

将数据写入文件为String

PrintWriter txt = new PrintWriter(out);
txt.print(pennies);
txt.close();

而不是out.write(pennies); 并将数据读取为

pennies = Integer.parseInt(in.readLine());

请记住，在运行程序之前，不要忘记将整数值存储在sub_total.txt

于 2011-02-20T18:20:25.573 回答