import javax.swing.*; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.io.*; class wj extends JFrame implements ActionListener { FileReader r_file; FileWriter w_file; BufferedReader buf_reader; BufferedWriter buf_writer; JTextArea txt; JButton an1,an2; JPanel p; wj() { setSize(200,200); setVisible(true); txt=new JTextArea(10,10); an1=new JButton("读取"); an2=new JButton("显示"); an1.addActionListener(this); an2.addActionListener(this); p=new JPanel(); add(txt,"center"); add(p,"south"); p.setLayout(new FlowLayout()); p.add(an1); p.add(an2); validate(); setDefaultCloseOperation(EXIT_ON_CLOSE); } public void actionPerformed(ActionEvent e) { if (e.getSource()==an1) { readFile(); } if (e.getSource()==an2) { writeFile(); } } public void readFile() { String s; try { File f=new File("D:/jtext/","input.txt"); r_file=new FileReader(f); buf_reader=new BufferedReader(r_file); } catch (IOException ef) { System.out.println(ef); } try { while ((s=buf_reader.readLine())!=null); { txt.append(s+'\n'); } } catch (IOException er) { System.out.println(er); } } public void writeFile() { try { w_file=new FileWriter("output.txt"); buf_writer=new BufferedWriter(w_file); String str= txt.getText(); buf_writer.write(str,0,str.length()); buf_writer.flush(); } catch (IOException ew) { System.out.println(ew); } } } public class 文件流 { public static void main(String[] args) { wj w=new wj(); } }修改代码使其在input中输入一段短文，统计文件中字符个数并将结果写入另一个文件output中

修改后的代码如下：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;

class WJ extends JFrame implements ActionListener {
    FileReader r_file;
    FileWriter w_file;
    BufferedReader buf_reader;
    BufferedWriter buf_writer;
    JTextArea txt;
    JButton an1, an2;
    JPanel p;

    WJ() {
        setSize(200, 200);
        setVisible(true);
        txt = new JTextArea(10, 10);
        an1 = new JButton("读取");
        an2 = new JButton("显示");
        an1.addActionListener(this);
        an2.addActionListener(this);
        p = new JPanel();
        add(txt, "center");
        add(p, "south");
        p.setLayout(new FlowLayout());
        p.add(an1);
        p.add(an2);
        validate();
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == an1) {
            readFile();
        }
        if (e.getSource() == an2) {
            writeFile();
        }
    }

    public void readFile() {
        String s;
        try {
            File f = new File("D:/jtext/", "input.txt");
            r_file = new FileReader(f);
            buf_reader = new BufferedReader(r_file);
        } catch (IOException ef) {
            System.out.println(ef);
        }
        try {
            while ((s = buf_reader.readLine()) != null) {
                txt.append(s + '\n');
            }
        } catch (IOException er) {
            System.out.println(er);
        }
    }

    public void writeFile() {
        try {
            w_file = new FileWriter("D:/jtext/output.txt");
            buf_writer = new BufferedWriter(w_file);
            String str = txt.getText();
            int length = str.length();
            buf_writer.write("字符个数为：" + length);
            buf_writer.flush();
        } catch (IOException ew) {
            System.out.println(ew);
        }
    }
}

public class 文件流 {
    public static void main(String[] args) {
        WJ w = new WJ();
    }
}

修改后的代码在读取按钮读取输入文件后，计算文件中字符个数并将结果写入output文件中。