Question

我刚读完'Java for Dummies'并开始创建一个简单的POS程序。我一直无法让程序按照我的意愿去做！我有两个actionListeners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，然后其他用于小计。我确实让小计工作加起来相同饮料的倍数，但不是'Amigos'和'Fosters'。这是通过尝试共享子总变量来编程的。我尝试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！下面是我的代码，试图实现我的读写工作。

这是我的第一个Java程序，所以请原谅我遇到的格式，标点符号和Java约定。也请原谅我缺乏评论。非常感谢任何建议！

此致

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;   
    }
}

Answer 1

您收到此错误，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。

Answer 2

正如Vivek说它应该解决你的问题。

但是你会得到NumberFormatException

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

但小计可以多个字符，（小计会在您增加项目数时增加）。

当小计超过一个字符时，它会在sub_total.txt文本文件

中写入垃圾值

Integer.parseInt(in.readLine());尝试将数据读取为String并将其解析为int

结果为NumberFormatException

解决方案：

将数据写为文件String

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

而不是out.write(pennies); 并将数据读作

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

请记住，在运行程序之前，请不要忘记在sub_total.txt

中存储整数值

FileNotFoundException问题

2 个答案: