为什么我的代码不起作用？

Question

This method is supposed to load the next question into a GUI.

public void readNextEntry() {

    list = new ArrayList<String>();

    scanner = new Scanner(linesFromFile.get(currentQuestion)).useDelimiter(",|\n");
    for (int i = 0; i < 8; i++) {
        list.add(scanner.next());
    }
}

The text file it is supposed to load from is as follows in the format:

001,what color is the sky,it is blue because of precipitation,green,blue,yellow,red,a,   
002,What color are my eyes,they are blue if you look,blue,brown,green,black,a,    
003,What color is the water,it is blue because of water,green,blue,red,yellow,b,

Why doesn't it work? It's supposed to load in, the category ( 001 ), the question ( what color is the sky? ), and the choices for it ( green,blue,yellow,red ). Is my regex off?

edit: a bit of context, this is the full code. Been trying suggestions from this thread with no success thus far.

package TestAssignment;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
import javax.swing.*;
import javax.swing.border.Border;

public class TestGui extends JFrame implements ActionListener {

private int counter = 0;
private int totalCount = 0;
private JTextArea question = new JTextArea();
private JTextArea recomendedAnswer = new JTextArea();
private JTextArea category = new JTextArea();
private ArrayList<String> list;
private ArrayList<String> linesFromFile;
private int currentQuestion = 0;
private ButtonGroup group = new ButtonGroup();
private ArrayList<JRadioButton> theButtons;
private JLabel response = new JLabel("");
private JButton answer = new JButton("Answer Question");
private Border border = BorderFactory.createLineBorder(Color.BLACK, 1);
private Scanner scanner;
private String fileName;

public void readNextEntry() {

    list = new ArrayList<String>();

    scanner = new Scanner(linesFromFile.get(currentQuestion)).useDelimiter(",|\n");
    for (int i = 0; i < 8; i++) {
        list.add(scanner.next());
    }
}

public void readFile() {
    linesFromFile = new ArrayList<String>();
    list = new ArrayList<String>();
    try {

        scanner = new Scanner(new File(fileName));
        while (scanner.hasNextLine()) {
            linesFromFile.add(scanner.nextLine());
        }
        Collections.shuffle(linesFromFile);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}

public TestGui(String in) {

    setLayout(new GridLayout(11, 25));
    this.fileName = in;

    add(new JLabel("Category : "));
    JScrollPane scrollPane1 = new JScrollPane(category);
    category.setLineWrap(true);
    category.setBorder(border);
    add(scrollPane1);
    category.setEditable(false);

    //int randomNumber = (int) (Math.random() * 10) + 1;
    //String line = TestGui.readFileByLine("Questions.txt", randomNumber);

    add(new JLabel("Question: "));
    JScrollPane scrollPane2 = new JScrollPane(question);
    question.setLineWrap(true);
    question.setBorder(border);
    add(scrollPane2);
    question.setEditable(false);

    readFile();
    readNextEntry();

    add(new JLabel("Please Select the correct Answer"));

    theButtons = new ArrayList<JRadioButton>();

    for (int i = 0; i < 4; i++) {
        JRadioButton temp = new JRadioButton();
        theButtons.add(temp);
        add(temp);
        group.add(temp);
    }
    refreshButtonLabels();

    add(response);

    category.setText(list.get(0));
    question.setText(list.get(1));

    add(answer);

    answer.addActionListener(this);
   }

  public void refreshButtonLabels() {
    for (int i = 0; i < 4; i++) {
        theButtons.get(i).setText(list.get(i + 3));
    }
  }

    @Override
    public void actionPerformed(ActionEvent e) {
    if (e.getSource() == answer) {
        for (int i = 0; i < theButtons.size(); i++) {
            JRadioButton button = theButtons.get(i);
            if (button.isSelected() && list.get(7).equals("a")) {
                counter++;
                readNextEntry();
            }
            else if (button.isSelected() && list.get(7).equals("b")){
                counter++;
                readNextEntry();
            }
             else if (button.isSelected() && list.get(7).equals("c")){
                counter++;
                readNextEntry();
            }
             else if (button.isSelected() && list.get(7).equals("d")){
                counter++;
                readNextEntry();

            }
        }
    }
     else {
           readNextEntry();
          {
    }
    }





package TestAssignment;

import javax.swing.JFrame;


public class Test {
public static void main(String[] args) {
    TestGui test = new TestGui();
    test.setVisible(true);
    test.setSize(600, 600);
    test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}
}

Answer 1

You'll find it much easier to simply split the string on commas:

String line = linesFromFile.get(currentQuestion);
String[] list = line.split(",\\s*");

The Scanner is just getting in your way. But when you do use a Scanner, never call one of its nextXXX() methods without first calling the associated hasNextXXX() method. For example:

while (scanner.hasNext())
{
  list.add(scanner.next());
}

Used correctly, Scanner should never throw a NoSuchElementException.

Answer 2

In theory this should work. The confusing thing was working out the types of variables that are only hinted at in your snippet.

static List<String> linesFromFile = new ArrayList<String>();
static {
    linesFromFile.add("001,what color is the sky,it is blue because of precipitation,green,blue,yellow,red,a,");
    linesFromFile.add("002,What color are my eyes,they are blue if you look,blue,brown,green,black,a,");
    linesFromFile.add("003,What color is the water,it is blue because of water,green,blue,red,yellow,b,");
}

public static void main(String[] args) {
    List<String> list = new ArrayList<String>();

    Scanner scanner = new Scanner(linesFromFile.get(1)).useDelimiter(",|\n");
    for (int i = 0; i < 8; i++) {
        list.add(scanner.next());
    }
    System.out.println(Arrays.toString(list.toArray()));
}

Prints [002, What color are my eyes, they are blue if you look, blue, brown, green, black, a]

Why are you delimitering by "\\n" if you have already have them separated by lines? Seems like one of the lines doesn't have enough elements like you are expecting. You should try outputting the line before getting the individual elements (or just debugging it).