java创建TXT文件并进行读、写、修改操作

前言：

　　 这周忙的连滚带爬的，终于在周末前把项目完工了。这次主要做的是一个UDP协议的转发器，是一个纯java写的程序，没有任何的框架在里面。其中为了保留住传进来的数据，我们用TXT文本记录下这些数据。文件代码传上来，需要的朋友直接下载就可以用。

代码：

import java.io.*;


/** *//**
 * 
 * 功能描述：创建TXT文件并进行读、写、修改操作
 *      
 * @author <a href="mailto:zhanghhui@126.com">KenZhang</a>
 * @version 1.0 
 * Creation date: 2007-12-18 - 下午06:48:45
 */
public class ReadWriteFile {
    public static BufferedReader bufread;
    //指定文件路径和名称
    private static String path = "D:/suncity.txt";
    private static  File filename = new File(path);
    private static String readStr ="";


    /** *//**
     * 创建文本文件.
     * @throws IOException 
     * 
     */
    public static void creatTxtFile() throws IOException{
        if (!filename.exists()) {
            filename.createNewFile();
            System.err.println(filename + "已创建！");
        }
    }
    
    /** *//**
     * 读取文本文件.
     * 
     */
    public static String readTxtFile(){
        String read;
        FileReader fileread;
        try {
            fileread = new FileReader(filename);
            bufread = new BufferedReader(fileread);
            try {
                while ((read = bufread.readLine()) != null) {
                    readStr = readStr + read+ "\r\n";
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        System.out.println("文件内容是:"+ "\r\n" + readStr);
        return readStr;
    }
    
    /** *//**
     * 写文件.
     * 
     */
    public static void writeTxtFile(String newStr) throws IOException{
        //先读取原有文件内容，然后进行写入操作
        String filein = newStr + "\r\n" + readStr + "\r\n";
        RandomAccessFile mm = null;
        try {
            mm = new RandomAccessFile(filename, "rw");
            mm.writeBytes(filein);
        } catch (IOException e1) {
            // TODO 自动生成 catch 块
            e1.printStackTrace();
        } finally {
            if (mm != null) {
                try {
                    mm.close();
                } catch (IOException e2) {
                    // TODO 自动生成 catch 块
                    e2.printStackTrace();
                }
            }
        }
    }
    
    /** *//**
     * 将文件中指定内容的第一行替换为其它内容.
     * 
     * @param oldStr
     *            查找内容
     * @param replaceStr
     *            替换内容
     */
    public static void replaceTxtByStr(String oldStr,String replaceStr) {
        String temp = "";
        try {
            File file = new File(path);
            FileInputStream fis = new FileInputStream(file);
            InputStreamReader isr = new InputStreamReader(fis);
            BufferedReader br = new BufferedReader(isr);
            StringBuffer buf = new StringBuffer();

            // 保存该行前面的内容
            for (int j = 1; (temp = br.readLine()) != null
                    && !temp.equals(oldStr); j++) {
                buf = buf.append(temp);
                buf = buf.append(System.getProperty("line.separator"));
            }

            // 将内容插入
            buf = buf.append(replaceStr);

            // 保存该行后面的内容
            while ((temp = br.readLine()) != null) {
                buf = buf.append(System.getProperty("line.separator"));
                buf = buf.append(temp);
            }

            br.close();
            FileOutputStream fos = new FileOutputStream(file);
            PrintWriter pw = new PrintWriter(fos);
            pw.write(buf.toString().toCharArray());
            pw.flush();
            pw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /** *//**
     * main方法测试
     * @param s
     * @throws IOException
     */
    public static void main(String[] s) throws IOException {
        ReadWriteFile.creatTxtFile();
        ReadWriteFile.readTxtFile();
        ReadWriteFile.writeTxtFile("20080808:12:13");
//        ReadWriteFile.replaceTxtByStr("ken", "zhang");
    }
}

清空txt文件的内容：

File f = new File("c:/abc.txt");
FileWriter fw =  new FileWriter(f);
fw.write("");fw.close();