io 基本操作

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1 Io

可以分为字节流字符流

例子字节流

读一个写一个

        //得到文件
       File file = new File("D:/test.txt");
       try {
              //把文件交个输入流
           FileInputStream in = new FileInputStream(file);
           //需要输出的
           FileOutputStream out = new FileOutputStream("D:/ttd.txt");
           int b =0;
           while((b=in.read())!=-1){
                  out.write(b);
           }
           out.flush();
            in.close();
            out.close();
      } catch (FileNotFoundException e) {
           System.out.println("找不到文件");
       } catch (IOException e) {
           System.out.println("读取文件失败");
       }
   }

2 先把数据读出来在写入

//得到文件
       File file = new File("D:/test.txt");
       try {
           //拿到文件给输入流
           FileInputStream in = new FileInputStream(file);
           byte[]ter = new byte[1024];
           //将文件读到数组中
           //in.read(ter);
           FileOutputStream out = new FileOutputStream("D:/tt.txt");
           //判断是否为空
           if(in.read(ter)!=-1) {
               //将数组的数据写进去txt 文件中
               out.write(ter);
           }
           out.flush();
           in.close();
           out.close();
       } catch (FileNotFoundException e) {
           System.out.println("找不到文件");
       } catch (IOException e) {
           System.out.println("文件读入失败");
       }

   }

字符流

//字符流
        File file = new File("D:/test.txt");
        try {
           FileReader re = new FileReader(file);
           //读取一个字符返回 int
           //如果为-1   结尾
           //re.read();
           int b =0;
           FileWriter   w = new FileWriter("D:/wr.txt");
           while((b= re.read())!=-1){
               w.write(b);
           }
           w.flush();
           re.close();
           w.close();

       } catch (FileNotFoundException e) {
           System.out.println("文件找不到");
           e.printStackTrace();
       } catch (IOException e) {
           // TODO Auto-generated catch block
            System.out.println("文件读入失败");
       }
   }

2 //字符流    存储到数组里
       File file = new File("D:/test.txt");
       try {
           FileReader   re = new FileReader(file);
           FileWriter wr = new FileWriter("D:/t3.txt");
           //定义数组并保存文件到数组中
           char[]c = new char[1024];
            int b =re.read(c);
           if(b!=-1){
               wr.write(c);
           }
           wr.flush();
           re.close();
           wr.close();

       } catch (FileNotFoundException e) {
           System.out.println("找不到");
           e.printStackTrace();
       } catch (IOException e) {
           System.out.println("错误");
           e.printStackTrace();
       }
   }

4 . 缓存流

    //缓存流
       File file = new File("D:/test.txt");
       InputStream in;
       try {
           in = new FileInputStream(file);
           BufferedInputStream   bf = new BufferedInputStream(in,1024);
             byte[]by = new byte[1024];
           OutputStream   out = new FileOutputStream("D:/t4.txt");
           BufferedOutputStream bfo = new BufferedOutputStream(out);
           if(bf.read(by)!=-1){
               bfo.write(by);
           }
           bfo.flush();
           bf.close();
           bfo.close();
       } catch (FileNotFoundException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       }
   }

缓存流的使用理解

先把一定大小的数据保存到一个小桶里面 read（）的时候会在里面拿到！减少了i/o ，否则去读取新的数据到缓冲区(通常比请求的数据要多)，

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