Python微信订餐小程序课程视频

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Python实战量化交易理财系统

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《零基础学Java》

• 带缓冲的输入/输入流

缓冲是 I/O 的一种性能优化。缓冲流为 I/O 流增加了内存缓冲区。

• BufferedInputStream类 与 BufferedOutputStream类

BufferedInputStream类 可以对所有InputStream的子类进行缓冲区的包装，以达到性能的优化。

BufferedOutputStream类 中的 flush()方法 被用来把缓冲区的字节写入到文件中，并清空缓存。

BufferedInputStream类的构造方法：

BufferedOutputStream类的构造方法：

BufferedInputStream类 与 BufferedOutputStream类 实例：

|  | import java.io.*; |
|  |  |
|  | public class Demo4 { |
|  | public static void main(String[] args) { |
|  | /** |
|  |  * 缓冲字节输入流（BufferedInputStream） |
|  |  * 特点：提高效率 |
|  |  */ |
|  | File file = new File("C:\\JAVA\_API\_1.7中文.chm"); |
|  | BufferedInputStream bufferedInputStream = null;//创建缓冲字节流 |
|  | FileInputStream fileInputStream = null; |
|  | long stare = System.currentTimeMillis();//获得当前流开始时的毫秒值 |
|  | try { |
|  |  fileInputStream=new FileInputStream(file); |
|  |  bufferedInputStream = new BufferedInputStream(fileInputStream);//将文件字节流包装成缓冲字节流 |
|  | byte by[] = new byte[1024];//缓冲区字节数组（这个缓冲区与Buffered不同） |
|  | while ((bufferedInputStream.read(by))!=-1){//使用缓冲字节流读取数据 |
|  |  |
|  |  } |
|  | long end = System.currentTimeMillis();//获得当前流结束时的毫秒值 |
|  |  System.out.println("运行经历的毫秒数："+(end - stare)); |
|  |  |
|  |  } catch (FileNotFoundException e) { |
|  |  e.printStackTrace(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } finally { |
|  | if (fileInputStream!=null){ |
|  | try { |
|  |  fileInputStream.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  | if (bufferedInputStream!=null){ |
|  | try { |
|  |  bufferedInputStream.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  |  } |
|  |  |
|  |  |
|  | /** |
|  |  * 缓冲字节输出流（BufferedOutputStream） |
|  |  * 特点：提高效率 |
|  |  */ |
|  | File file1 = new File("C:\\Word.txt"); |
|  | BufferedOutputStream bufferedOutputStream = null;//创建缓冲字节输出流 |
|  | FileOutputStream fileOutputStream = null; |
|  | try { |
|  |  fileOutputStream=new FileOutputStream(file1); |
|  |  bufferedOutputStream=new BufferedOutputStream(fileOutputStream);//将文件输出流包装到缓冲字节输出流 |
|  |  |
|  | String str = "深山踏红叶，耳畔闻鹭鸣。"; |
|  | byte by[] = str.getBytes(); |
|  |  bufferedOutputStream.write(by); |
|  | //<*> 使用缓冲字节输出流时，要多进行刷新操作，避免等待，有数据时就将数据写入文件当中 <*> |
|  |  bufferedOutputStream.flush();//刷新（强制将缓冲区数据写入文件中，即使缓冲区没有写满） |
|  |  |
|  |  } catch (FileNotFoundException e) { |
|  |  e.printStackTrace(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } finally { |
|  | if (fileOutputStream!=null){ |
|  | try { |
|  |  fileOutputStream.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  | if (bufferedOutputStream!=null){ |
|  | try { |
|  |  bufferedOutputStream.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  |  } |
|  |  } |
|  | } |

• BufferedReader类 与 BufferedWriter类

BufferedReader类 与 BufferedWriter类 分别继承了 Reader类 与 Writer类，这两个类同样具有内部缓冲机制，并以行为单位输入/输出。

BufferedReader类常用方法：

BufferedWriter类常用方法：

BufferedReader类 与 BufferedWriter类 实例：

|  | import java.io.*; |
|  |  |
|  | public class Demo6 { |
|  | public static void main(String[] args) { |
|  | File file = new File("C:\\Word.txt"); |
|  |  |
|  | /** |
|  |  * 文件缓冲字符输出流（BufferedWriter） |
|  |  */ |
|  | FileWriter fileWriter = null;//创建文件字符输出流 |
|  | BufferedWriter bufferedWriter = null;//创建文件缓冲字符输出流 |
|  |  |
|  | try { |
|  |  fileWriter = new FileWriter(file); |
|  |  bufferedWriter = new BufferedWriter(fileWriter);//将文件字符输出流包装成文件缓冲字符输出流 |
|  |  |
|  | String str1 = "神里"; |
|  | String str2 = "绫华"; |
|  |  |
|  |  bufferedWriter.write(str1);//第一行数据 |
|  |  bufferedWriter.newLine();//创建一个新行 |
|  |  bufferedWriter.write(str2);//第二行数据 |
|  |  |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  }finally {//<*> 注意：流的关闭顺序，先创建的后关闭。 <*> |
|  | if (bufferedWriter!=null){ |
|  | try { |
|  |  bufferedWriter.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  | if (fileWriter!=null){ |
|  | try { |
|  |  fileWriter.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  |  } |
|  |  |
|  |  |
|  | /** |
|  |  * 文件缓冲字符输入流（BufferedReader） |
|  |  */ |
|  | FileReader fileReader = null; |
|  | BufferedReader bufferedReader = null; |
|  | try { |
|  |  fileReader = new FileReader(file); |
|  |  bufferedReader = new BufferedReader(fileReader);//将文件字符输入流包装成文件缓冲字符输入流 |
|  | String tmp = null;//临时变量 |
|  | int i = 1;//计数器 |
|  | while ((tmp = bufferedReader.readLine())!=null){//循环读取文件中的内容 |
|  |  System.out.println("第"+i+"行："+tmp); |
|  |  i++; |
|  |  } |
|  |  } catch (FileNotFoundException e) { |
|  |  e.printStackTrace(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } finally { |
|  | if (bufferedReader!=null){ |
|  | try { |
|  |  bufferedReader.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  | if (fileReader!=null){ |
|  | try { |
|  |  fileReader.close(); |
|  |  } catch (IOException e) { |
|  |  e.printStackTrace(); |
|  |  } |
|  |  } |
|  |  } |
|  |  } |
|  | } |

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