java基础之IO流的应用

字节流

 (1)IO流体系

  IO流

   |--字节流

         |--输入流

                    InputStream

                   FileInputStream

                  BufferedInputStream//高效读取

         |--输出流

                OutputStream

                 FileOutputStream

                 BufferedOutputStream//高
4000
效写入

  |--字符流
         |--输入流

                Reader

                FileReader

               BufferedReader//高效读取

        |--输出流

               Writer

               FileWriter

               BufferedWrite//高效写入

 打印流：PrintWriter, PrintStream

 对象序列化流： ObjectInputStream,

  对象反序列化流 ：ObjectOutputStream

代码一：复制文本

   BufferedReader br = new BufferedReader(new FileReader("a.txt"));

   BufferedWriter bw = new BufferedWriter(new FileWriter("b.txt"));

  String line = null;

  while((line=br.readLine())!=null)

  {

   bw.write(line);

   bw.newLine();

   bw.flush();

  }

  bw.close();

  br.close();

    代码二：复制图片

  FileInputStream fis = new FileInputStream("a.jpg");//源，用字节流

  FileOutputStream fos = new FileOutputStrema("b.jpg");//

  byte[] bys = new byte[1024];

  int len = 0;

  while((len=fis.read(bys))!=-1)

  {

   fos.write(bys,0,len);

  }

  fos.close();

  fis.close();

 代码三：把文件中的数据输入到控制台

  public static void main(String[] args) throws IOException {

  BufferedReader br = new BufferedReader(new FileReader("fos.txt"));

  BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(

    System.out));

  String line = null;

  while ((line = br.readLine()) != null) {

   bw.write(line);

   bw.newLine();

   bw.flush();

  }

  bw.close();

  br.close();

 }

  代码四：从键盘录入数据打印在控制台

 

 键盘录入:

 System.in -- InputStream -- 转换流 -- InputStreamReader

 控制台输出:

 System.out -- OutputStream -- 转换流 -- OutputStreamWriter

  
public class ConsoleDemo {

 public static void main(String[] args) throws IOException {

  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

  BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(

    System.out));

  String line = null;

  while ((line = br.readLine()) != null) {

   if ("over".equals(line)) {

    break;

   }

   bw.write(line);

   bw.newLine();

   bw.flush();

  }

  bw.close();

  br.close();

 }