Question

我写了这篇日记，用户可以选择日期，为该日期写一些文字并保存。文本存储在每个日期的哈希表中。

我现在正在尝试将哈希表保存在文件中。关于我写的代码我几乎没有问题：

代码无效，有些错误我不明白：

线程中的异常＆＃34; main＆＃34; java.io.EOFException的

at java.io.ObjectInputStream$PeekInputStream.readFully(Unknown Source)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(Unknown Source)
at java.io.ObjectInputStream.readStreamHeader(Unknown Source)
at java.io.ObjectInputStream.<init>(Unknown Source)
at Q2.MainPanel.updateHashFromFile(MainPanel.java:133)
at Q2.MainPanel.<init>(MainPanel.java:46)
at Q2.Main.main(Main.java:13)

eclipse总是警告我要为每个写一些处理文件的方法添加抛出。我认为这样做的方式是正确的吗？
是否像我一样将FileInputStream，ObjectInputStream，File声明为全局参数？或者有更多推荐的方式吗？
您认为在同一个类中一起编写面板和GUI处理和数据以及像我一样保存处理的好方法吗？或者将这些分成几类更好？

这是代码：

package Q2;
import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Hashtable;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class MainPanel extends JPanel{

    private String[] days = {"1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22","23","24","25","26","27","28","29","30","31"};
    private String[] months = {"1","2","3","4","5","6","7","8","9","10","11","12"};
    private String[] years = {"2014","2015","2016","2017","2018"};
    private Font myFont = new Font("david", Font.BOLD, 24);
    JButton btnSave, btnShow;
    JComboBox daysBox,yearsBox,monthsBox;
    private static Hashtable<MyDate, String> diary;
    private JTextArea textArea;
    private static File file;
    private static FileInputStream in;
    private static FileOutputStream out;
    private static ObjectInputStream streamIn;
    private static ObjectOutputStream streamOut;

    //Constructor for main panel with BorderLayout with panels inside
    public MainPanel () throws IOException, ClassNotFoundException{
        this.setLayout(new BorderLayout());
        add(getDateButtons(),BorderLayout.NORTH);
        textArea = new JTextArea();
        textArea.setFont(myFont);
        add(textArea, BorderLayout.CENTER);
        add(getSaveShowButtons(),BorderLayout.SOUTH);

        file = new File("MyDiary");
        updateHashFromFile();


        diary = new Hashtable<MyDate, String>();
    }

    //create and return the NORTH date buttons panel
    private JPanel getDateButtons(){
        JPanel dateButtons = new JPanel();

        //create and add the days JCombobox
        daysBox = new JComboBox(days);
        daysBox.setFont(myFont);
        dateButtons.add(daysBox);

        //create and add the months JCombobox
        monthsBox = new JComboBox(months);
        monthsBox.setFont(myFont);
        dateButtons.add(monthsBox);

        //create and add the year JCombobox
        yearsBox = new JComboBox(years);
        yearsBox.setFont(myFont);
        dateButtons.add(yearsBox);

        return dateButtons;
    }

    //
    private JPanel getSaveShowButtons(){
        JPanel saveShowButtons = new JPanel();
        ButtonListener lis = new ButtonListener();

        btnSave = new JButton("save");
        btnSave.addActionListener(lis);
        btnSave.setFont(myFont);
        saveShowButtons.add(btnSave);

        btnShow = new JButton("show");
        btnShow.addActionListener(lis);
        btnShow.setFont(myFont);
        saveShowButtons.add(btnShow);

        return saveShowButtons;

    }

    private class ButtonListener implements ActionListener{


        @Override
        public void actionPerformed(ActionEvent e) {
            if (e.getSource()==btnSave){
                int day = Integer.parseInt((String)daysBox.getSelectedItem());
                int month = Integer.parseInt((String)monthsBox.getSelectedItem());
                int year = Integer.parseInt((String)yearsBox.getSelectedItem());
                MyDate date = new MyDate(day, month, year);
                System.out.println(date);
                diary.put(date,textArea.getText());
                textArea.setText(null);
                try {
                    updateHashToFile();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
            if (e.getSource()==btnShow){
                int day = Integer.parseInt((String)daysBox.getSelectedItem());
                int month = Integer.parseInt((String)monthsBox.getSelectedItem());
                int year = Integer.parseInt((String)yearsBox.getSelectedItem());
                MyDate date = new MyDate(day, month, year);
                String s = diary.get(date);
                if (s!=null)
                    textArea.setText(s+" ");
                else textArea.setText(" ");
            }

        }
    }

    @SuppressWarnings("unchecked")
    private static void updateHashFromFile() throws IOException, ClassNotFoundException{
        if(!file.exists())
            file.createNewFile();
        else {
            in = new FileInputStream(file);
            streamIn = new ObjectInputStream(in);
            diary = (Hashtable<MyDate, String>)streamIn.readObject();
        }

    }

    //update the file with the new hash table diary data
    private static void updateHashToFile() throws IOException{
        out = new FileOutputStream(file);
        streamOut = new ObjectOutputStream(out);
        streamOut.writeObject(diary);
    }
}

MyDate类代码：

package Q2;

public class MyDate {

    private static int[] numOfDays = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; //Number of days on each month
    private int day;
    private int month;
    private int year;

    //Constructor for date object
    public MyDate(int day, int month, int year){
        if(day<=numOfDays[month-1]){ //In case chosen day that not exist in the month the last day of the month will be chosen
            this.day = day;
        }else this.day = numOfDays[month-1];
        this.month = month;
        this.year = year;
    }

    //@override toString
    public String toString(){
        return this.day+"/"+ this.month+"/"+this.year;
    }

    //@override equals
    public boolean equals(Object other){
        if(this.day==((MyDate)other).day && this.month==((MyDate)other).month && this.year==((MyDate)other).year)
            return true;
        return false;
    }


    public int hashCode() {
        return ((day * 31) + month) * 31 + year; 
    }
}

主类代码：

package Q2;
import java.io.IOException;

import javax.swing.JFrame;

public class Main {

    public static void main(String[] args) throws IOException, ClassNotFoundException{
        JFrame frame = new JFrame("Diary");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(700, 700);
        frame.setLocationRelativeTo(null);
        MainPanel mainPanel = new MainPanel();
        frame.add(mainPanel);

        frame.setVisible(true);
    }
}

Answer 1

我没有收到任何警告，但ClassNotFoundException异常看起来没用。
避免对流使用静态变量。您可以在此特定代码中本地声明它们，但这不是规则。相反，你可以声明静态最终的日期，月份和年份，因为它们是常量而且永远不会改变。
这是您的选择，取决于代码最终的清晰程度。

请务必关闭蒸汽。

这是修改后的代码和我的建议。我暂时用java.util.Date替换了MyDate，所以我可以编译代码，你可以忽略它。

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileInputStream;
//import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Hashtable;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class MainPanel extends JPanel{

    private static final String[] days = {"1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22","23","24","25","26","27","28","29","30","31"};
    private static final String[] months = {"1","2","3","4","5","6","7","8","9","10","11","12"};
    private static final String[] years = {"2014","2015","2016","2017","2018"};
    private static final Font myFont = new Font("david", Font.BOLD, 24);
    JButton btnSave, btnShow;
    JComboBox daysBox,yearsBox,monthsBox;
    private Hashtable<java.util.Date, String> diary;
    private JTextArea textArea;
    private File file;

    //Constructor for main panel with BorderLayout with panels inside
    public MainPanel () throws IOException, ClassNotFoundException{
        this.setLayout(new BorderLayout());
        add(getDateButtons(),BorderLayout.NORTH);
        textArea = new JTextArea();
        textArea.setFont(myFont);
        add(textArea, BorderLayout.CENTER);
        add(getSaveShowButtons(),BorderLayout.SOUTH);

        file = new File("MyDiary");
        updateHashFromFile();


        diary = new Hashtable<java.util.Date, String>();
    }

    //create and return the NORTH date buttons panel
    private JPanel getDateButtons(){
        JPanel dateButtons = new JPanel();

        //create and add the days JCombobox
        daysBox = new JComboBox(days);
        daysBox.setFont(myFont);
        dateButtons.add(daysBox);

        //create and add the months JCombobox
        monthsBox = new JComboBox(months);
        monthsBox.setFont(myFont);
        dateButtons.add(monthsBox);

        //create and add the year JCombobox
        yearsBox = new JComboBox(years);
        yearsBox.setFont(myFont);
        dateButtons.add(yearsBox);

        return dateButtons;
    }

    //
    private JPanel getSaveShowButtons(){
        JPanel saveShowButtons = new JPanel();
        ButtonListener lis = new ButtonListener();

        btnSave = new JButton("save");
        btnSave.addActionListener(lis);
        btnSave.setFont(myFont);
        saveShowButtons.add(btnSave);

        btnShow = new JButton("show");
        btnShow.addActionListener(lis);
        btnShow.setFont(myFont);
        saveShowButtons.add(btnShow);

        return saveShowButtons;

    }

    private class ButtonListener implements ActionListener{


        @Override
        public void actionPerformed(ActionEvent e) {
            if (e.getSource()==btnSave){
                int day = Integer.parseInt((String)daysBox.getSelectedItem());
                int month = Integer.parseInt((String)monthsBox.getSelectedItem());
                int year = Integer.parseInt((String)yearsBox.getSelectedItem());
                java.util.Date date = new java.util.Date(day, month, year);
                System.out.println(date);
                diary.put(date,textArea.getText());
                textArea.setText(null);
                try {
                    updateHashToFile();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
            if (e.getSource()==btnShow){
                int day = Integer.parseInt((String)daysBox.getSelectedItem());
                int month = Integer.parseInt((String)monthsBox.getSelectedItem());
                int year = Integer.parseInt((String)yearsBox.getSelectedItem());
                java.util.Date date = new java.util.Date(day, month, year);
                String s = diary.get(date);
                if (s!=null)
                    textArea.setText(s+" ");
                else textArea.setText(" ");
            }

        }
    }

    @SuppressWarnings("unchecked")
    private void updateHashFromFile() throws IOException, ClassNotFoundException{
        if(!file.exists())
            file.createNewFile();
        else {
            FileInputStream in = new FileInputStream(file);
            ObjectInputStream streamIn = new ObjectInputStream(in);
            diary = (Hashtable<java.util.Date, String>)streamIn.readObject();
            streamIn.close();
        }

    }

    //update the file with the new hash table diary data
    private void updateHashToFile() throws IOException{
        FileOutputStream out = new FileOutputStream(file);
        ObjectOutputStream streamOut = new ObjectOutputStream(out);
        streamOut.writeObject(diary);
        streamOut.close();
    }
}

Java Hashtable保存到文件中

1 个答案: