io流读写及相关内容

列出某个目录下的所有文件：

File file = new File("e:\总结");
File[] files = file.listFiles();
for(int i=0; i<files.length; i++){
 if(files[i].isFile()) System.out.println(files[i]);
}

列出某个目录下的所有子目录：

File file = new File("e:\总结");
File[] files = file.listFiles();
for(int i=0; i<files.length; i++){
 if(files[i].isDirectory()) 
 System.out.println(files[i]);
}

如何读写文件，代码如下，有读取，复制，写入：

public class ReadWriteCopy {
    public static void main(String args[]) {
        String from = "h:\Android\readtext.txt";
        String to = "h:\Android\writetext.txt";
        readline(from);
        copyText(from,to);
        writeText(to);
        //deletefile(from);
    }

    public static void deletefile(String from){
        File fromFile=new File(from);
        if(fromFile.exists()){
            fromFile.delete();
        }        
    }
    public static void readline(String from) {
        File fromFile = new File(from);
        BufferedReader reader=null;    
        //FileReader fr=null;//可以用这个
        if (fromFile.exists()) {
            try {        
                //InputStreamReader isr=new InputStreamReader(new DataInputStream(new FileInputStream(fromFile)),"gb2312");
                //或者
                InputStreamReader isr=new InputStreamReader(new BufferedInputStream(new FileInputStream(fromFile),1024),"gb2312");
                reader=new BufferedReader(isr);
                List<users> userList=new ArrayList<users>();
                String row="";
                while ((row=reader.readLine()) != null) {    
                    users u=new users();
                    String[] text=row.split(",");
                    u.setUserName(text[0]);
                    u.setUserId(text[1]);
                    u.setUserDate(text[2]);
                    userList.add(u);
                }
                for(users u:userList){
                    System.out.println("用户名："+u.getUserName()+"id:"+u.getUserId()+"date:"+u.getUserDate());
                }
            }catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }finally{
                try {
                    reader.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            } 
        }
    }
    
    public static void copyText(String from,String to){
        File fromFile = new File(from);
        File toFile = new File(to);
        BufferedInputStream fis=null;
        BufferedOutputStream fos=null;
        try {
            fis=new BufferedInputStream(new FileInputStream(fromFile));
            fos=new BufferedOutputStream(new FileOutputStream(toFile));
            
            int num;
            while((num=fis.read())!=-1){
                fos.write(num);
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            try {
                fis.close();
                fos.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }            
        }
        
    }
    
    public static void writeText(String to){
        String text="往txt文件里写入该字符串";
        File toFile = new File(to);
        FileOutputStream fos=null;
        FileWriter fw=null;
        try {
            fos=new FileOutputStream(toFile);
            fos.write(text.getBytes());
            
            fw=new FileWriter(toFile);
            fw.write(text);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}