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();
 }