java - 数组列表出现问题

在WordPair（）类中，方法remove（）应该接收一个数组并拆分其中的字符串，然后将这些字符串添加到两个不同的数组列表中。 wordListB可以正常工作，并且数组可以很好地填充。同样，当我在此方法内部进行系统打印时，它也会正确打印出wordListC。当在JlistFromFile类的wordSelection方法中调用getWord方法以从worldListC的特定索引中检索字符串时，遇到了我遇到的问题，此时数组打印为空。我在主体中设置了一个测试，该类本身正在按预期工作。我不知道是什么使arrayListC被清除。

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.util.Collections;
import java.util.Arrays;

import java.io.*;

/* Simple example of using the contents of a file to populate a JList
 *
 * @author Jill Courte
 */

public class JListFromFile extends JFrame {

  private TextField wordA;
  private TextField wordB;
  private JButton openButton;
  private JButton newButton;
  private JButton addButton;
  private JButton deleteButton;
  private JButton saveButton;
  private TextField output;
  private JList listFromFile;
  private JPanel listPanel;
  private JPanel textPanel;
  private JPanel inputPanel;
  private JPanel buttonsPanel;
  private SimpleWordList dataSource;
  private WordPair wordPair;
  public JListFromFile ()
  {
    // create the object to provide the data
    dataSource = new SimpleWordList();
    wordPair = new WordPair();
    // use a border layout for the main window
    getContentPane().setLayout(new BorderLayout(20, 20));

    buttonsPanel = new JPanel();
    openButton = new JButton("Open");
    newButton = new JButton("New");
    addButton = new JButton("Add");
    deleteButton = new JButton("Delete");
    saveButton = new JButton("Save");
    addButton.setEnabled( false );
    deleteButton.setEnabled( false );
    saveButton.setEnabled( false );
    buttonsPanel.add(openButton);
    buttonsPanel.add(newButton);
    buttonsPanel.add(addButton);
    buttonsPanel.add(deleteButton);
    buttonsPanel.add(saveButton);

    //add the button listeners
    openButton.addActionListener(new OpenButtonListener());
    addButton.addActionListener(new AddButtonListener());

    add(buttonsPanel, BorderLayout.NORTH);

    // create the panel to hold the list
    listPanel = new JPanel();

    // create your JList
    listFromFile = new JList();
    listFromFile.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
    listFromFile.setSelectedIndex(0);

    //add the list selection listener
   listFromFile.addListSelectionListener(new WordSelection());

    //add the translation text box
    textPanel = new JPanel();
    output = new TextField();
    output.setEditable(false);
    output.setPreferredSize(new Dimension(200, 25));
    textPanel.add(output);

    // add scroll bars to list
    JScrollPane listScrollPane = new JScrollPane(listFromFile);
    listScrollPane.setPreferredSize(new Dimension(150, 200));

    //add user input textfield
    wordA = new TextField ("Word to Add");
    wordB = new TextField ("Translated word");
    wordA.setPreferredSize(new Dimension(200, 25));
    wordB.setPreferredSize(new Dimension(200, 25));
    wordA.setEnabled(false);
    wordB.setEnabled(false);

    //create panel to hold input textfield
    inputPanel = new JPanel();
    inputPanel.add(wordA);
    inputPanel.add(wordB);

    //add the list (via the scroll pane) to the panel
    listPanel.add(listScrollPane);

    //add the panels to the frame
    add(listPanel, BorderLayout.WEST);
    add(textPanel, BorderLayout.CENTER);
    add(inputPanel, BorderLayout.SOUTH);
    pack();
  }


  private File findFile ()
  {
    JFileChooser chooser = new JFileChooser();

    chooser.setFileSelectionMode(JFileChooser.FILES_ONLY);

    // Start in current directory
    chooser.setCurrentDirectory(new File("."));
    int status = chooser.showOpenDialog(null);

    if (status != JFileChooser.APPROVE_OPTION)
    {
      JOptionPane.showMessageDialog(null, "No File Selected");
      throw new NoFileChoosenException();
    }
    else
    {
      File file = chooser.getSelectedFile();

      System.out.println(file.getName());
      System.out.println(file.getPath());


      return file;
    }
  }


  private class OpenButtonListener implements ActionListener
  {
    public void actionPerformed (ActionEvent event)
    {

      listFromFile.setListData(new Object[0]);

      File file = null;

      try
      {
        file = findFile();

        //tell the data source what file to use
        dataSource.createList(file);

        //JList needs an array of strings, retrieve it from the data source
        String [] data = dataSource.getData();

        //data = dataSource.insertion(data);
        //data = wordPair.remove(data);
        if (data != null)
        listFromFile.setListData(data);

      }
      catch (Exception e)
      {
      }
      addButton.setEnabled(true);
      deleteButton.setEnabled(true);
      saveButton.setEnabled(true);
      wordA.setEnabled(false);
      wordB.setEnabled(false);
    }
  }

  private class AddButtonListener implements ActionListener
  {
    public void actionPerformed (ActionEvent event)
    {


      wordA.setEnabled(true);
      wordB.setEnabled(true);

      String inputStringA = wordA.getText();
      String inputStringB = wordB.getText();



      //dataSource.addToList(inputStringA, inputStringB);

      String [] data2 = dataSource.getData();
      //data2 = dataSource.insertion(data2);
       // data2 = wordPair.remove(data2);
        listFromFile.setListData(new Object[0]);
        listFromFile.setListData(data2);


    }
  }

  private class WordSelection implements ListSelectionListener
     {
      public void valueChanged (ListSelectionEvent event)
      {
          int index = listFromFile.getSelectedIndex();
          if (index >= 0)
          {
           String s = wordPair.getWord(index);
           output.setText(s);
          }
      }
     }

  public static void main(String[] args)
  {
    JListFromFile jListFromFile = new JListFromFile();
    jListFromFile.setVisible(true);
  }
}

import java.io.FileInputStream;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Scanner;
import java.util.ListIterator;

/*example of using collection class and input parsing for CIT 271
 *@author Jill Courte
 */

public class SimpleWordList {

 private ArrayList<String> wordListA = new ArrayList<String>();
 private ArrayList<String> wordListB = new ArrayList<String>();
 private ArrayList<String> wordListC = new ArrayList<String>();
 private File currentFile = null;
 private WordPair wordPair;
 //words are in the file one word on a line
 //words are read, checked for duplicates, and inserted into the file




 public void createList (File file)
 {
     Scanner fileIn = null;
     currentFile = file;
     String line;

     try
     {
         fileIn = new Scanner(new FileInputStream(currentFile.getPath()));
     }
     catch (IOException e)
     {
       System.out.println(e.getMessage());
       System.exit(0);
     }


     while (fileIn.hasNextLine())
     {
        line = fileIn.nextLine();
        if (! isDuplicate(line))
            insertIntoList(line);
     }

     fileIn.close();
 }

 //Uses an iterator to check for the existance of the given
 //word in the list
 private boolean isDuplicate (String word)
 {
    Iterator<String> it = wordListA.iterator();
    while (it.hasNext())
    {
        //not ignoring case to look in class at some issues with input
        String s = it.next();
        if (word.equals(s))
            return true;
    }

    return false;
 }

 private void insertIntoList (String word)
 {
    int index = 0;
    boolean positionFound = false;
    int result;

    while (! positionFound && index < wordListA.size())
    {
        String tmp = wordListA.get(index);

        result = tmp.compareTo(word);
        if (result > 0)
            positionFound = true;
        else
            index++;
    }

    //index holds the position to insert the word

    wordListA.add(index, word);

    //System.out.println(word);
  }


 public String [] getData ()
    {
        String [] arr = new String[wordListA.size()];

        wordPair = new WordPair();
        String [] temp2 = wordPair.remove(wordListA.toArray(arr));

        // use the collection class method to turn this into a
        // primitive array
        return temp2;
    }
}




import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Scanner;
import java.util.ArrayList;
import java.util.*;
public class WordPair
{
   private ArrayList<String> wordListB;
  private ArrayList<String> wordListC;
  private String [] arrayA;
  private String [] arrayB;
  private String wordA;
  private String wordB;


   public  String[] remove (String numList[])
   {
     wordListB = new ArrayList<String>();
     wordListC = new ArrayList<String>();
     ArrayList<String> ar = new ArrayList<String>();
     for( int i=0; i < numList.length; i++)
     {
       String string = numList[i];
       String[] parts = string.split("=");

       wordA = parts[0];
       wordListB.add(wordA);
       wordB = parts[1];
       wordListC.add(wordB);

       }
      System.out.println(wordListC);
     arrayA = wordListB.toArray(new String[wordListB.size()]);

     return arrayA;

   }

   public String getWord(int index)
   {
     System.out.println(wordListC);
     return wordListC.get(index);
   }

}

最佳答案

在您的JListFromFile类中，您创建一个WordPair字段wordPair，但是您从不提供我可以看到的任何数据。因此，对我来说这将是空的。

是的，您在调用getData()时提供了一个WordPair对象数据，但它与JListFromFile对象所持有的WordPair对象不同。而是由SimpleWordList变量dataSource保留的WordPair对象。

也许您希望两个对象共享同一个WordPair对象，如果是这样，则只需编写一些代码即可：

wordPair = new WordPair();
dataSource = new SimpleWordList(wordPair); // note the parameter

别处

class SimpleWordList {

   private ArrayList<String> wordListA = new ArrayList<String>();
   private ArrayList<String> wordListB = new ArrayList<String>();
   private ArrayList<String> wordListC = new ArrayList<String>();
   private File currentFile = null;
   private WordPair wordPair;

   // note the assignment constructor
   public SimpleWordList(WordPair wordPair) {
      this.wordPair = wordPair;
   }

和其他地方：

public String[] getData() {
  String[] arr = new String[wordListA.size()];

  // ****** don't create a new object -- use the one we have ***
  //  wordPair = new WordPair();  ****** don't create a new one!

  String[] temp2 = wordPair.remove(wordListA.toArray(arr));

  // use the collection class method to turn this into a
  // primitive array
  return temp2;
}