Java IO（三）- 处理流

处理流

1，缓冲流

缓冲流要“套接”在相应的节点流之上，对读写的数据提供了缓冲的功能，提高了读写的效率，同时增加了一些新的方法。

J2SDK提供了四种缓冲流，其常用的构造方法：

BufferedReader
BufferedReader(Reader in)
Creates a buffering character-input stream that uses a default-sized input buffer.
BufferedReader(Reader in, int sz)
Creates a buffering character-input stream that uses an input buffer of the specified size.

BufferedWriter
BufferedWriter(Writer out)
Creates a buffered character-output stream that uses a default-sized output buffer.
BufferedWriter(Writer out, int sz)
Creates a new buffered character-output stream that uses an output buffer of the given size.

BufferedInputStream
BufferedInputStream(InputStream in)
Creates a BufferedInputStream and saves its argument, the input stream in, for later use.
BufferedInputStream(InputStream in, int size)
Creates a BufferedInputStream with the specified buffer size, and saves its argument, the input stream in, for later use.

BufferedOutputStream
BufferedOutputStream(OutputStream out)
Creates a new buffered output stream to write data to the specified underlying output stream.
BufferedOutputStream(OutputStream out, int size)
Creates a new buffered output stream to write data to the specified underlying output stream with the specified buffer size.

缓冲输入流支持其父类的mark和reset方法
BufferedReader提供了readLine方法用于读取一行字符串(以\r或\n分隔)
BufferedWriter提供了newLine方法用于写入一个行分隔符
对于输出的缓冲流，写出的数据会先在内存中缓存，使用flush方法将会使内存中的数据立刻写出。

例子一

    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("d:\\share\\java\\HelloWorld.java");
            BufferedInputStream bis = new BufferedInputStream(fis);
            int c = 0;
            System.out.println(bis.read());
            System.out.println(bis.read());
            bis.mark(100);
            for(int i = 0; i <= 10 && (c=bis.read()) != -1; i++) {
                System.out.print((char)c + " ");
            }
            System.out.println();
            bis.reset();
            for(int i = 0; i <= 10 && (c=bis.read()) != -1; i++) {
                System.out.print((char)c + " ");
            }
            bis.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

结果：

4742

 a l ; s k j d f ; 

 a l ; s k j d f ; 

例子二、

    public static void main(String[] args) {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter("d:\\dat2.txt"));
            BufferedReader br = new BufferedReader(new FileReader("d:\\dat2.txt"));
            String s = null;
            for(int i = 1; i<=100; i++) {
                s = String.valueOf(Math.random());
                bw.write(s);
                bw.newLine();
            }
            bw.flush();
            while((s = br.readLine()) != null) {//读一行
                System.out.println(s);
            }
            bw.close();
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

结果：

dat2.txt文件：

控制台输出：