IO流读写数据示例

• 常用的字节输入流有：InputStream ,FileInputStream,BufferedInputStream

• 常用的字节输出流有：OutputStream,FileOutputStream,BufferedOutputStream 
• 常见的字符输入流有：Reader,InputStreamReader,FileReader,BufferedReader
• 常见的字符输出流有：Writer,OutputStreamWriter,FileWriter,BufferedWriter
• Buffered修饰的流是缓存的流，信息从内存中操作，效率比一般流操作效率高  

demo如下：

public class Iotest {
    public static void main(String[] args) {
        File file = new File("E:\\iotest\\wl.txt");
        /*
         * 字节流 向文件中保存内容
         */
        try (OutputStream os = new FileOutputStream(file, true)) {
            String str = "\r\n hello world";
            byte[] ss = str.getBytes("UTF-8");
            os.write(ss);
        } catch (IOException e) {
            e.printStackTrace();
        }
        /*
         * 字节流 BufferedInputStream 向文件中保存信息
         */
        try (BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file, true))) {
            String str2 = "\r\n buffered hello world";
            byte[] bytes = str2.getBytes("UTF-8");
            bos.write(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
         * 字节流 从文件中读取文件信息
         * */
        try (InputStream inputStream = new FileInputStream(file)) {
            byte[] input = new byte[1024];
            int len = 0;
            while ((len = inputStream.read(input)) != -1) {
                System.out.println(new String(input, 0, len));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
         * 字节流 BufferInputStream 从文件中读取内容
         * */
        try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file))) {
            int len = 0;
            byte[] bytes = new byte[1024];
            while ((len = bis.read(bytes)) != -1) {
                System.out.println(new String(bytes, 0, len));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }


        /*
         * 字符流 向文件中保存信息
         * */
        try (Writer writer = new FileWriter(file, true)) {
            String str2 = "\r\n 你好 中国！";
            writer.write(str2);
            writer.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
         * 字符流 BufferWriter 向文件中保存内容
         * */
        try (BufferedWriter bw = new BufferedWriter(new FileWriter(file, true))) {
            bw.write("\r\n Buffered 你好 中国!");
            bw.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
         * 字符流 读取文件中信息
         * */
        try (Reader reader = new FileReader(file)) {
            char[] r = new char[1024];
            int len = 0;
            while ((len = reader.read(r)) != -1) {
                System.out.println(new String(r, 0, len));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
         * 字符流 BufferReader 从文件中读取信息
         * */
        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
            String line = "";
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}