为什么不读?

时间:2011-03-24 00:19:55

标签: java

我想问一下我的程序有什么问题.. 我的程序是关于堆栈的,它没有错误,但我的问题是,我们的要求是在堆栈中执行所有操作然后,即使你关闭程序,下次打开它时,仍然应该显示以前的数据.. 我使用了文件编写器和文件读取器,但每次关闭它,然后再次打开它,之前的数据不会出现.. 有什么建议? 谢谢..这是我的程序..

import java.util.*;
import java.awt.*;
import java.io.*;
import javax.swing.*;
import java.awt.event.*;
public class STACKS extends JFrame implements ActionListener
{
    private JButton push,pop,peek,display,exit;
    private JLabel Stack;
    static int arr[],x=0,b=0,xy=0,c=0;
    static String in="",INDEX="",d="",s="";
    static String id[]={};

    public STACKS()
    {
        super("STACKS MENU!^_^");
        Container c=getContentPane();
        c.setLayout(new FlowLayout());
        Stack=new JLabel("STACKS MENU!^_^");    c.add(Stack);
        push=new JButton("Push!^-^");
        pop=new JButton("Pop!^-^");
        peek=new JButton("Peek!^-^");
        display=new JButton("Display!^-^");
        exit=new JButton("Exit!^-^");
        push.addActionListener(this);           c.add(push);
        pop.addActionListener(this);            c.add(pop);
        peek.addActionListener(this);           c.add(peek);
        display.addActionListener(this);        c.add(display);
        exit.addActionListener(this);           c.add(exit);
        setVisible(true);
        setSize(150,250);
    }
    public static void saveMe() throws IOException
    {
        File data1=new File("Sample.txt");      //a file was created...
        PrintWriter out=new PrintWriter(new BufferedWriter(new FileWriter(data1,true)));
        for(int x=0;x<4;x++)
        {
            out.write(":"+arr[x]);  xy=1;           //here in this section, I put : in every elements inside the array..
        }
        out.close();

    }
    public static void readMe() throws IOException
    {
        Scanner txtFile=(new Scanner("Sample.txt"));

        for(int y=0;x<id.length;y++)
        {
            s=txtFile.nextLine();
            id=s.split(":");
            arr[y]=Integer.parseInt(id[y]);
        }

    }
    public  void actionPerformed(ActionEvent a)
    {
        try
        {
            readMe();                               //here is where the previous data will be read..
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null,"File not found! readme !^,^");
        }
        if (xy==0)
        {
            INDEX=JOptionPane.showInputDialog(null,"Enter LENGTH of the array!");
            c=Integer.parseInt(INDEX); xy=1;
            arr=new int[c];
        }
        if(a.getSource()==push)
        {
            in=JOptionPane.showInputDialog(null,"Enter integer to be pushed!");
            b=Integer.parseInt(in);
            arr[x]=b;   x+=1;
            if(x==c)
            {
                JOptionPane.showMessageDialog(null,"WARNING! The stacks are full, please pop something!^-^");
            }
            if(x>c)
            {
                JOptionPane.showMessageDialog(null,"Sorry, the stacks are full,please pop something first!^-^");
                x-=1;
            }
        }
        else if(a.getSource()==pop)
        {

            arr[x-1]=0;x-=1;
            JOptionPane.showMessageDialog(null,"The value has been popped!^-^");
            if(x==0)
            {
                JOptionPane.showMessageDialog(null,"The stacks are empty, push something!^-^");
            }

        }
        else if(a.getSource()==peek)
        {
            JOptionPane.showMessageDialog(null,"The value is "+arr[x-1]+"! ^-^");
        }
        else if(a.getSource()==display)
        {
            for(int y=c-1;y>-1;y--)
            {
                d+="*** "+arr[y]+" ***\n";
            }
            JOptionPane.showMessageDialog(null,"The value inside the stacks are:\n"+d);
            d="";
        }
        else if(a.getSource()==exit)
        {
            System.exit(0);
        }
            try
        {
            saveMe();                   //here is where the file will be saved..
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null,"File not found!^,^");
        }
    }
    public static void main(String args[])
    {
        STACKS pot=new STACKS();
        pot.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }
}

3 个答案:

答案 0 :(得分:1)

实际上这里有很多问题。

就亚历山大的答案而言,你会在每次推/拉电话后保存,因此正在调用saveMe()

但是,在saveMe()中,您在堆栈的第一个元素之前编写:,因此将其读回将始终提供额外的空白元素。在写:之前检查x!= 0。

readMe()中,您为id.length调用nextLine(),这在两个方面有误:

  1. 启动程序时,id的长度为零。您不应该使用x<id.length作为for循环的结束条件(无论如何x都是错误的,它应该在您的上下文中为y)。使用txtFile.hasNext()检查是否还有更多要读取的堆栈元素。
  2. 您的文件完全包含一行,而不是多行。您应该做的是将扫描仪的分隔符设置为: textFile.useDelimiter(":"),然后调用next()。还要记住,除非你更正saveMe(),否则在开头会有一个额外的元素是空白的。
  3. 同样在readMe(),根据Nicklamort的回答,您需要致电new Scanner(new File("Sample.txt"))打开实际文件。

    readMe()

    的示例
    public static void readMe() throws IOException
    {
        Scanner txtFile=(new Scanner(new File("Sample.txt")));
        int y = 0;
        txtFile.useDelimiter(":");
        while(txtFile.hasNext())
        {
            arr[y]=txtFile.nextInt();
            y++;
        }
    
    }
    

    saveMe()

    的示例
    public static void saveMe() throws IOException
    {
        File data1=new File("Sample.txt");      //a file was created...
        PrintWriter out=new PrintWriter(new BufferedWriter(new FileWriter(data1,false))); // don't append, overwrite existing data since we are saving the entire stack each time
        for(int x=0;x<arr.length;x++)
        {
            if(x != 0) { out.write(":"); }           //here in this section, I put : in every elements inside the array..
            out.write(arr[x]);  xy=1;
        }
        out.flush(); // force writing to disk
        out.close();
    }
    

答案 1 :(得分:1)

当您尝试从文件中读取时:

Scanner txtFile=(new Scanner("Sample.txt"));

我认为您正在尝试解析文字字符串:“Sample.txt”

您希望将实际文件对象传递给Scanner构造函数:

Scanner txtFile = new Scanner(File source);

查看docs

答案 2 :(得分:0)

因为您在致电System.exit

之前致电saveMe()

在终止程序之前必须调用FileWriter.close,这样缓冲区输出就会被刷新到磁盘。