读取文本文件并回写数据怎么实现？

[干饭人之路]

我知道读取文件可以这样：

import java.io.*;

public class ReadFile {
 public static void main(String[] args) throws FileNotFoundException, IOException {    
FileReader myFileReader=new FileReader("d:/javatest/dsstatic_20090427.f"); 

BufferedReader myBufferedReader=new BufferedReader(myFileReader);


String myString=null; 

String resultString=new String(); 

while((myString=myBufferedReader.readLine())!=null) 
{ System.out.println(myString);
} 
myFileReader.close();

}
}

但是要实现对某一特定行回写数据应该怎么做？
比如，发现myString中有txt字符串，把这个字符串改写为txt123,并回写到那一行，代码应该怎么写？

[bayougeng]

用RandomAccessFile可以实现。

[gutan_fox]

等待~

[ruisheng_412]

FileReader 对应Filewrite

BufferedReader 对应 BufferedWrite

[dajiadebeibei9]

你用的BufferedReader写入 对应的应该是BufferedWriter
可以这样初始化 BufferedWriter bw = new BufferedWriter(new FileWriter("输出文件路径"));
如果发现字符串里面有txt 可以用repalceAll()方法
具体是这样的：StringBuffer sb = new StringBuffer("要传入的字符串");
sb = sb.replaceAll("txt","txt123");

[EM265]

public static void main(String[] args) throws Exception{
		//如果a.txt文件中包函 txt 则会把 txt 替换成txt123 ,楼主可试试，看是不是你所想要的那种
		String filePath = "c:/tmp/a.txt";	
		String tmpFile = "c:/tmp/"+System.currentTimeMillis()+".txt";	
		copyFile(filePath,tmpFile);		
		BufferedInputStream bis = new BufferedInputStream(new FileInputStream(tmpFile));
		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(filePath)); 
		byte[] b = new byte[1024];
		int c =0;
		while((c=bis.read(b)) > 0){
			String s = new String(b).replaceAll("txt", "txt123");
			bos.write(s.getBytes());
		}
		bis.close();
		bos.close();
		//删除临时文件
		new File(tmpFile).delete();
	}
	
	/**复制文件*/
	private static void copyFile(String sourceFile,String targetFile)throws Exception{
		BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceFile));
		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(targetFile));
		byte[] by = new byte[1024];
		int c=0;
		while((c = bis.read(by))> 0){
			bos.write(by);
		}
		bos.close();		
		bis.close();	
	}