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Java之IO流详解（三）——字符流-创新互联

一、概述

Writer 是写入字符流的抽象类。
OutputStreamWriter（OutputStream out）：输出转换流，创建使用默认字符编码的OutputStreamWriter。
OutputStreamWriter（OutputStream out, String charsetName）：创建使用指定字符编码的OutputStreamWriter。
字符流的底层还是用字节流进行读写的，字符流仅仅是做了字节和字符的转换。

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Reader是用于读取字符流的抽象类。
InputStreamReader(InputStream in)：输入转换流，创建默认字符集的InputStreamReader。
InputStreamReader(InputStream in, String charsetName)：创建使用指定字符编码的InputStreamReader。

二、字符流写数据
  • 字符流写文本数据
方法说明
publicvoid write(int c)写出一个字符
publicvoid write(char[] cbuf)写出字符数组
publicvoid write(char[] cbuf, int off, int len)写出字符数组cbuf中，从off开始，共len个字符
publicvoid write(String str)写出字符串
publicvoid write(String str, int off, int len)写出字符串，从off开始，共len个字符

eg:

//publicvoid write(int c) 写出一个字符
public static void main(String[] args) {OutputStreamWriter outputStreamWriter = null;
    try {outputStreamWriter = new OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test02.txt"), "UTF-8");
        outputStreamWriter.write('a');
        outputStreamWriter.write('b');
        outputStreamWriter.write('c');
        outputStreamWriter.write('猫');
    } catch (IOException e) {e.printStackTrace();
    } finally {if (outputStreamWriter != null) {try {outputStreamWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
//publicvoid write(char[] cbuf, int off, int len) 写出字符数组cbuf中，从off开始，共len个字符
public static void main(String[] args) {OutputStreamWriter outputStreamWriter = null;
    try {outputStreamWriter = new OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test02.txt"), "UTF-8");
        char[] chars = {'a','b','c','猫'};
        outputStreamWriter.write(chars,2,2);
    } catch (IOException e) {e.printStackTrace();
    } finally {if (outputStreamWriter != null) {try {outputStreamWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
//publicvoid write(char[] cbuf) 写出字符数组
public static void main(String[] args) {OutputStreamWriter outputStreamWriter = null;
    try {outputStreamWriter = new OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test02.txt"), "UTF-8");
        char[] chars = {'a','b','c','猫'};
        outputStreamWriter.write(chars);
    } catch (IOException e) {e.printStackTrace();
    } finally {if (outputStreamWriter != null) {try {outputStreamWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
//publicvoid write(String str) 写出字符串
public static void main(String[] args) {OutputStreamWriter outputStreamWriter = null;
    try {outputStreamWriter = new OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"),"UTF-8");
        outputStreamWriter.write("好好学习，天天向上");
    } catch (IOException e) {e.printStackTrace();
    }finally {if(outputStreamWriter != null){try {outputStreamWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
//publicvoid write(String str, int off, int len) 写出字符串，从off开始，共len个字符
public static void main(String[] args) {OutputStreamWriter outputStreamWriter = null;
    try {outputStreamWriter = new OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"),"UTF-8");
        outputStreamWriter.write("好好学习，天天向上", 4, 4);
    } catch (IOException e) {e.printStackTrace();
    }finally {if(outputStreamWriter != null){try {outputStreamWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
三、字符流读数据
方法说明
int read()一次读一个字符数据
int read(char[] cbuf)一次读一个字符数组数据

eg：

//int read() 一次读一个字符数据
public static void main(String[] args) {InputStreamReader inputStreamReader = null;
    try {inputStreamReader = new InputStreamReader(new FileInputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"), "UTF-8");
        System.out.println((char)inputStreamReader.read());
        System.out.println((char)inputStreamReader.read());
        System.out.println((char)inputStreamReader.read());
    } catch (IOException e) {e.printStackTrace();
    }finally {if(inputStreamReader != null){try {inputStreamReader.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
//int read(char[] cbuf) 一次读一个字符数组数据
public static void main(String[] args) {InputStreamReader inputStreamReader = null;
    try {inputStreamReader = new InputStreamReader(new FileInputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"),"UTF-8");
        char[] chars = new char[1024];
        int length;
        while ((length = inputStreamReader.read(chars)) != -1){System.out.println(new String(chars,0,length));
        }

    } catch (IOException e) {e.printStackTrace();
    }finally {if(inputStreamReader != null){try {inputStreamReader.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
四、字符流拷贝文本文件

eg:

public static void main(String[] args) {  InputStreamReader inputStreamReader = null;
	  OutputStreamWriter outputStreamWriter = null;
	  try {  inputStreamReader = new InputStreamReader(new FileInputStream("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"));
	      outputStreamWriter = new OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\Desktop\\test\\test02\\test01.txt"));
	      char[] chars = new char[1024];
	      int length;
	      while ((length = inputStreamReader.read(chars)) != -1){  outputStreamWriter.write(chars,0, length);
	      }
	  } catch (IOException e) {  e.printStackTrace();
	  }finally {  if(inputStreamReader != null){  try {  inputStreamReader.close();
	          } catch (IOException e) {  e.printStackTrace();
	          }
	      }
	      if(outputStreamWriter != null){  try {  outputStreamWriter.close();
	          } catch (IOException e) {  e.printStackTrace();
	          }
	      }
	  }
}

五、FileWriter和FileReader
eg:

public static void main(String[] args) {FileReader fileReader = null;
    FileWriter fileWriter = null;
    try {fileReader = new FileReader("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt");
        fileWriter = new FileWriter("C:\\Users\\Administrator\\Desktop\\test\\test02\\test01.txt");
        char[] chars = new char[1024];
        int length;
        while ((length = fileReader.read(chars)) != -1){fileWriter.write(chars,0,length);
        }
    } catch (IOException e) {e.printStackTrace();
    }finally {if(fileReader != null){try {fileReader.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
        if(fileWriter != null){try {fileWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
六、字符缓冲流
  1. 概述

（1）BufferedReader：字符缓存输入流。从字符输入流读取文本，缓冲各个字符，从而实现字符、数组和行的高效读取。
FileReader：内部使用InputStreamReader，解码过程，byte ->char，默认缓存大小为8K。
BufferedReader：默认缓存大小为8K，但可以手动指定缓存大小，把数据读取到缓存中，减少每次转换过程，效率更高。
（2）BufferedWriter：字符缓存输出流。将文本写入字符输出流，缓存各个字符，从而提供单个字符、数组和字符串的高效写入。
FileWriter：内部使用InputStreamWriter，解码过程，byte ->char，默认缓存大小为8K。
BufferedWriter：默认缓存大小为8K，但可以手动指定缓存大小，把数据读取到缓存中，减少每次转换过程，效率更高。
（3）字符缓冲流与字节缓冲流的思想一样。

  1. 字符缓冲流的读写操作
    eg：
public static void main(String[] args) {//写数据
    BufferedWriter bufferedWriter = null;
    try {bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"));
        bufferedWriter.write("好好学习，天天向上");
    } catch (IOException e) {e.printStackTrace();
    }finally {if(bufferedWriter != null){try {bufferedWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
    //读数据
    BufferedReader bufferedReader = null;
    try {bufferedReader = new BufferedReader(new FileReader("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"));
        char[] chars = new char[1024];
        int length;
        while ((length = bufferedReader.read(chars)) != -1){System.out.println(new String(chars,0,length));
        }
    } catch (IOException e) {e.printStackTrace();
    }finally {if(bufferedReader != null){try {bufferedReader.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}
  1. 字符缓冲流的换行操作

（1）BufferedWriter

方法说明
void newLine()写一行分隔符，行分隔符字符串由系统属性定义

（2）BufferedReader

方法说明
String readLine()读一行文字。结果包含行的内容的字符串，不包括任何行终止字符，如果流的结尾已经到达，则返回null

eg：

public static void main(String[] args) {//写数据
    BufferedWriter bufferedWriter = null;
    try {bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"));
        for(int i=1; i<=10; i++){bufferedWriter.write("qizekj"+i);
            bufferedWriter.newLine();
        }
    } catch (IOException e) {e.printStackTrace();
    } finally {if (bufferedWriter != null) {try {bufferedWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
    //读数据
    BufferedReader bufferedReader = null;
    try {bufferedReader = new BufferedReader(new FileReader("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"));
        String str;
        while ((str = bufferedReader.readLine()) != null) {System.out.println(str);
        }
    } catch (IOException e) {e.printStackTrace();
    } finally {if (bufferedReader != null) {try {bufferedReader.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }

    }
}
  1. 字符缓冲流复制文本文件

eg：

public static void main(String[] args) {BufferedReader bufferedReader = null;
    BufferedWriter bufferedWriter = null;
    try {bufferedReader = new BufferedReader(new FileReader("C:\\Users\\Administrator\\Desktop\\test\\test01\\test01.txt"));
        bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\Desktop\\test\\test02\\test01.txt"));
        String str;
        while ((str = bufferedReader.readLine()) != null) {bufferedWriter.write(str);
            bufferedWriter.newLine();
        }
    } catch (IOException e) {e.printStackTrace();
    } finally {if (bufferedReader != null) {try {bufferedReader.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
        if (bufferedWriter != null) {try {bufferedWriter.close();
            } catch (IOException e) {e.printStackTrace();
            }
        }
    }
}

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