问一个java文件读写问题

[miaohw2002]

一个txt文件，我把内容读了出来更改后怎么写回去替换原来内容

给点代码提示谢谢

[redlaputa]

import java.io.*;
import java.util.*;

class p2
{
public static void main(String[] args)
{
try
{


BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream("p1.java")));
DataOutputStream dos=new DataOutputStream(new FileOutputStream("pp.java"));
String str;Object o;
//while(br.ready())
while((str=br.readLine())!=null)
{

l.add(str);
//System.out.println(str);
}
//ListIterator it=l.listIterator();
int i=1;
while ((o=l.removeLast())!=null)
{
System.out.println((String)o);
dos.writeBytes(i+" "+(String)o+"\n");
i++;
}



while(it.hasNext())
{
System.out.println((String)it.next());
}
while(it.hasPrevious())
{
System.out.println((String)it.previous());
}
*/
//System.out.println("Hello World!");
}
catch (Exception e)
{
}

}
}

[smallMage]

用BufferedReader读文件，用BufferedWrite写到文件里就可以呢

[miaohw2002]

2楼的你的l是什么l.add(str);

[miaohw2002]

BufferedWrite我写的怎么是追加呢？

[registered]

FileOutputStream
public FileOutputStream(File file,
boolean append)
throws FileNotFoundExceptionCreates a file output stream to write to the file represented by the specified File object. If the second argument is true, then bytes will be written to the end of the file rather than the beginning. A new FileDescriptor object is created to represent this file connection.
First, if there is a security manager, its checkWrite method is called with the path represented by the file argument as its argument.

If the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason then a FileNotFoundException is thrown.


Parameters:
file - the file to be opened for writing.
append - if true, then bytes will be written to the end of the file rather than the beginning
Throws:
FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason
SecurityException - if a security manager exists and its checkWrite method denies write access to the file.
Since:
1.4
See Also:
File.getPath(), SecurityException, SecurityManager.checkWrite(java.lang.String)


使用这个构造函数创建对象
用 append = false;

[andunkafei]

读出原文件内容并修改完后将原来的文件删除，然后将新文件保存为原来的文件名即可。