InputStream 和OutputStream，两个是为字节流设计的,主要用来处理字节或二进制对象；
Reader 和 Writer 两个是为字符流（一个字符占两个字节，字节缓冲区把字节先转换为字符）设计的，主要用来处理字符或字符串

具体见http://blog.csdn.net/zxman660/article/details/7875799

public class IOTest {
    public static void main(String[] args) throws Exception {

        /**
         * 字符流和字节流的区别，确保txt内数据既有中文又有英文
         */
        /*BufferedReader in = new BufferedReader(new InputStreamReader(
                new FileInputStream("/users/shao/Documents/file/SHA1.txt")));
        BufferedInputStream bufferedInputStream = new BufferedInputStream(
                new FileInputStream("/users/shao/Documents/file/SHA1.txt"));

        //System.out.println(in.readLine());
        int i = 0;
        while (i != -1) {
            i = in.read();
            System.out.print((char) i);
        }
        System.out.println();
        i = 0;
        while (i != -1) {
            i = bufferedInputStream.read();
            System.out.print((char) i);
        }*/

        /**
         * 追加的方式
         */
        File outfile = new File("/users/shao/Desktop/xlx.txt");
        FileOutputStream outputStream = new FileOutputStream(outfile, true);
        FileWriter out = new FileWriter(outfile, true);

        if (outfile.length() != 0) {
            out.write("\r\n");
            out.flush();                //不写会出顺序问题，和缓冲区有关
        }
        
        String str1 = "Hello ";
        String str2 = "World!";

        byte[] bytes = str1.getBytes();
        outputStream.write(bytes);
        out.write(str2);
        
        outputStream.close();
        out.close();

        /**
         * InputStream与OutputStream的使用例子
         *
         * (缓冲文件输入流)BufferedInputStream → (文件输入流)FileInputStream → (输入流)java.io.InputStream
         *
         * (缓冲文件输出流)BufferedOuputStream → (文件输出流)FileOuputStream → (输出流)java.io.OutputStream
         */

        /**
         * 1.通过流复制一个图片的例子
         */

        /*File file = new File("/users/shao/Documents/file/SHA1.txt");
        File outfile = new File("/users/shao/Desktop/xlx.txt");

        FileInputStream inputStream = new FileInputStream(file);
        FileOutputStream outputStream = new FileOutputStream(outfile);

        int i = 0;
        while (i != -1) {
            i = inputStream.read();
            outputStream.write(i);
        }
        //注意流的关闭(★必须的)
        inputStream.close();
        outputStream.close();*/

        /**
         * 2.如果我们想提高要提高复制的速度，可以采用缓冲文件输入\输出流，如下：
         */
        /*File file = new File("/users/shao/Documents/file/SHA1.txt");
        File outfile = new File("/users/shao/Desktop/xlx.txt");

        //文件输入流
        FileInputStream inputStream = new FileInputStream(file);
        //文件输出流
        FileOutputStream outputStream = new FileOutputStream(outfile);

        //缓冲文件输入流
        BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
        //缓冲文件输出流
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);

        int i = 0;
        while (i != -1) {
            i = bufferedInputStream.read();
            bufferedOutputStream.write(i);
        }
        //流的关闭
        bufferedOutputStream.flush();//强制清除缓冲区的内容
        bufferedInputStream.close();
        bufferedOutputStream.close();*/

        /**
         * 3.当文件很大,我们要做一个缓冲处理来提高速度。如下：当文件的大小大于512个字节时，每次读入512个字节后再做处理
         *
         */
        /*File file = new File("/users/shao/Documents/file/SHA1.txt");
        File outfile = new File("/users/shao/Desktop/xlx.txt");

        //文件输入流
        FileInputStream inputStream = new FileInputStream(file);
        //文件输出流
        FileOutputStream outputStream = new FileOutputStream(outfile);

        int i = 0;
        //缓冲大小为512字节
        byte[] buffer = new byte[512];
        while(true) {
            if(inputStream.available() < 512) {
                while(i != -1) {
                    i = inputStream.read();
                    outputStream.write(i);
                }
                break;//注意此处不能忘记哦
            } else {
                //当文件的大小大于512字节时
                inputStream.read(buffer);
                outputStream.write(buffer);
            }
        }

        //流的关闭
        //注意流的关闭(★必须的)
        inputStream.close();
        outputStream.close();*/

        /**
         * 4.根据上面的例子，我们可以知道：我们可以做一个双缓冲的文件复制
         */
        /*File file = new File("/users/shao/Documents/file/SHA1.txt");
        File outfile = new File("/users/shao/Desktop/xlx.txt");

        //文件输入流
        FileInputStream inputStream = new FileInputStream(file);
        //文件输出流
        FileOutputStream outputStream = new FileOutputStream(outfile);

        //缓冲文件输入流
        BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
        //缓冲文件输出流
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);

        int i = 0;
        //缓冲区的大小
        byte[] buffer = new byte[512];

        while(true) {
            if(bufferedInputStream.available() < 512) {
                while(i != -1) {
                    i = bufferedInputStream.read();
                    bufferedOutputStream.write(i);
                }
                break;
            } else {
                //当文件的大小还大于512字节时
                bufferedInputStream.read(buffer);
                bufferedOutputStream.write(buffer);

            }
        }

        //强制清空缓冲区的内容
        bufferedOutputStream.flush();
        //流的关闭
        bufferedInputStream.close();
        bufferedOutputStream.close();*/

    }
}