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();