Java AWT-EventQueue-0 不知道为什么还通过文本文件读取

Question

只是尝试打印第 31 行的 LOL，或者任何人都有更好的方法从下面保存的文本文件中返回余额。请随意分享，我在这个问题上陷入了困境。出现错误:

"Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at TopUpScreen.Reading(TopUpScreen.java:35)
    at TopUpScreen.balanceAmmount(TopUpScreen.java:56)
    at TopUpScreen$2.actionPerformed(TopUpScreen.java:183)"

如果有人知道为什么，我可能会做一些非常愚蠢的事情。但我无法找出为什么会发生这种情况。

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

class TopUpScreen extends JDialog
{
    private JPanel mainPanel;
    Boolean errormsg = false;
    String errorMessage = "";
    String safetyMessage = "";


public static String Reading(String FileName, String Returned) {
    try {
        ArrayList<String> Trains = new ArrayList<String>();
         String[] arrayed_line = null;
        int count = 0;
        //int count1 = 1;
        //String[] Returned = ;
        File file = new File(FileName);
        FileReader fileReader = new FileReader(file);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        StringBuffer stringBuffer = new StringBuffer();
        String line;
        while ((line = bufferedReader.readLine()) != null) 
        {
            if(line.matches(Returned)){
                System.out.println("LOL");

            }
            stringBuffer.append(line);
            arrayed_line[count] = line;
            count ++;
            Trains.add(line + "\n");
            stringBuffer.append("\n");

        }
        fileReader.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

    System.out.println();
    //return Returned;    
    return FileName;



}
    public void balanceAmmount(String name){
        String balance = null;
        balance = Reading("TopUp.txt", name);
        //System.out.println(balance);
        //return balance;
    }
public static void WriterFile(String data,String filetype)
{   
    try{
        //String data = " This content will append to the end of the file";

        File file = new File(filetype);

        //if file doesnt exists, then create it
        if(!file.exists()){
            file.createNewFile();
        }

        //true = append file
        FileWriter fileWritter = new FileWriter(file.getName(),true);
            BufferedWriter bufferWritter = new BufferedWriter(fileWritter);
            bufferWritter.write(data);
            bufferWritter.close();

        //System.out.println("Done");

    }catch(IOException e){
        e.printStackTrace();
    }
}
public TopUpScreen()
{

    setPanels();

    setModalityType(ModalityType.APPLICATION_MODAL);
    setSize(400, 350);
    setVisible(true);
}

JLabel ammount = new JLabel("Top Up Ammount: $");
JLabel name = new JLabel("Name:");
JLabel billingAddress = new JLabel("Billing Address:");
JLabel cardNumber = new JLabel("Card Number:");
JLabel cardName = new JLabel("Card Name:");
JLabel expiryDate = new JLabel("Expirary Date:");
JLabel errorField = new JLabel();

JTextField ammountField = new JTextField();
JTextField nameField = new JTextField();
JTextField billingAddressField = new JTextField();
JTextField cardNameField = new JTextField();
JTextField cardNumberField = new JTextField();
JTextField expiryDateField = new JTextField();
public void setPanels()
{
    mainPanel = new JPanel(new GridLayout(0, 2));
    JPanel containerPanel = new JPanel(new GridLayout(0, 1));
    JPanel lowerPanel = new JPanel(new FlowLayout());
    JPanel errorPanel = new JPanel(new FlowLayout());
    JButton apply = new JButton("PAY");
    JButton cancel = new JButton("Cancel");
    cancel.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            dispose();
        }
    });
    apply.addActionListener(new ActionListener()
    {

        public void actionPerformed(ActionEvent e)
        { 
            errorMessage= "";
            safetyMessage= "";

            String timestamp = new java.text.SimpleDateFormat("MM/dd/yyyy h:mm:ss a").format(new Date());
            String ammountS = ammountField.getText();
            String nameS = nameField.getText();
            String billingAddressS = billingAddressField.getText();
            String cardNameS = cardNameField.getText();
            String cardNumberS = cardNumberField.getText();
            String expiryDateS = expiryDateField.getText();

            if(ammountS.matches("[a-zA-Z]+")){
                safetyMessage += "Top Ammount invalid<br/>";
            }else{errorMessage += "";}
            if(ammountS == null || ammountS.isEmpty()){
                safetyMessage += "Please Enter an Ammount!<br/>";
            }else{errorMessage += "";}
            if(nameS == null || nameS.isEmpty()){
                safetyMessage += "Please Enter an Name!<br/>";
            }else{errorMessage += "";}
            if(billingAddressS == null || billingAddressS.isEmpty()){
                safetyMessage += "Please Enter a Billing Address!<br/>";
            }else{errorMessage += "";}
            if(cardNameS == null || cardNameS.isEmpty()){
                safetyMessage += "Please Enter a Card Name!<br/>";
            }else{errorMessage += "";}
            if(cardNumberS == null || cardNumberS.isEmpty()){
                safetyMessage += "Please Enter a Card Number!<br/>";
            }else{errorMessage += "";}
            if(expiryDateS == null || expiryDateS.isEmpty()){
                safetyMessage += "Please Enter a Expiry Date!<br/>";
            }else{errorMessage += "";}

            if (safetyMessage == ""){
                errorMessage += "Successfully Topped Up With: $"+ ammountS;
                errorField.setText(errorMessage);
                errormsg = true;
            }else{
                errorMessage += "<html>";
                errorMessage += safetyMessage;
                errorMessage += "</html>";
                errorField.setText(errorMessage);
            }

            if (errormsg == true){
            WriterFile("######## START OF TRANSACTION ########\n","TopUp.txt");
            WriterFile("Name: "+ nameS+"\n","TopUp.txt");
            WriterFile("DATE: "+ timestamp+"\n","TopUp.txt");
            WriterFile("Ammount: "+ ammountS+"\n","TopUp.txt");
            WriterFile("CardName: "+ cardNameS+"\n","TopUp.txt");
            WriterFile("Address: "+ billingAddressS+"\n","TopUp.txt");
            WriterFile("Card Number: "+ cardNumberS+"\n","TopUp.txt");
            WriterFile("ExpiryDate: "+ expiryDateS+"\n","TopUp.txt");
            WriterFile("######## END OF TRANSACTION ########\n","TopUp.txt");

            topUpAlertWindow TopUpAlertWindow = new topUpAlertWindow();
                balanceAmmount(nameS);
            //dispose();
            }
        }
    });
    mainPanel.add(ammount);
    mainPanel.add(ammountField);
    mainPanel.add(name);
    mainPanel.add(nameField);
    mainPanel.add(billingAddress);
    mainPanel.add(billingAddressField);
    mainPanel.add(cardName);
    mainPanel.add(cardNameField);
    mainPanel.add(cardNumber);
    mainPanel.add(cardNumberField);
    mainPanel.add(expiryDate);
    mainPanel.add(expiryDateField);

    errorPanel.add(errorField);

    lowerPanel.add(apply);
    lowerPanel.add(cancel);


    containerPanel.add(mainPanel);
    containerPanel.add(lowerPanel);
    containerPanel.add(errorPanel);

    add(containerPanel);
}
}

Answer 1

您的数组 arrayed_line 从未初始化。

您必须使用固定值对其进行初始化。

String[] arrayed_line = new String[5];

我认为这在你的解决方案中是不可能的。所以你必须使用ArrayList