字符流的示例代码

FileReader类的read()方法可以按照字符大小读取

• FileReader fr = new FileReader("aaa.txt");              //创建输入流对象,关联aaa.txt
  int ch;
  while((ch = fr.read()) != -1) {                         //将读到的字符赋值给ch
      System.out.println((char)ch);                       //将读到的字符强转后打印
  }
  
  fr.close();                                             //关流
  

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FileWriter类的write()方法可以自动把字符转为字节写出

FileWriter fw = new FileWriter("aaa.txt");
fw.write("aaa");
fw.close();

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字符流的拷贝

FileReader fr = new FileReader("a.txt");
FileWriter fw = new FileWriter("b.txt");

int ch;
while((ch = fr.read()) != -1) {
    fw.write(ch);
}

fr.close();
fw.close();

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自定义字符数组的拷贝

• FileReader fr = new FileReader("aaa.txt");          //创建字符输入流,关联aaa.txt
  FileWriter fw = new FileWriter("bbb.txt");          //创建字符输出流,关联bbb.txt
  
  int len;
  char[] arr = new char[1024*8];                      //创建字符数组
  while((len = fr.read(arr)) != -1) {                 //将数据读到字符数组中
      fw.write(arr, 0, len);                          //从字符数组将数据写到文件上
  }
  
  fr.close();                                         //关流释放资源
  fw.close(); 
  

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带缓冲的字符流

• BufferedReader的read()方法读取字符时会一次读取若干字符到缓冲区, 然后逐个返回给程序, 降低读取文件的次数, 提高效率
• BufferedWriter的write()方法写出字符时会先写到缓冲区, 缓冲区写满时才会写到文件, 降低写文件的次数, 提高效率

• BufferedReader br = new BufferedReader(new FileReader("aaa.txt"));  //创建字符输入流对象,关联aaa.txt
  BufferedWriter bw = new BufferedWriter(new FileWriter("bbb.txt"));  //创建字符输出流对象,关联bbb.txt
  
  int ch;             
  while((ch = br.read()) != -1) {     //read一次,会先将缓冲区读满,从缓冲去中一个一个的返给临时变量ch
      bw.write(ch);                   //write一次,是将数据装到字符数组,装满后再一起写出去
  }
  
  br.close();                         //关流
  bw.close();  
  

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readLine()和newLine()方法

• BufferedReader的readLine()方法可以读取一行字符(不包含换行符号)
• BufferedWriter的newLine()可以输出一个跨平台的换行符号" "

• BufferedReader br = new BufferedReader(new FileReader("aaa.txt"));
  BufferedWriter bw = new BufferedWriter(new FileWriter("bbb.txt"));
  String line;
  while((line = br.readLine()) != null) {
      bw.write(line);
      //bw.write("
  ");                 //只支持windows系统
      bw.newLine();                       //跨平台的
  }
  
  br.close();
  bw.close();  
  

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使用指定的码表读写字符

• FileReader是使用默认码表读取文件, 如果需要使用指定码表读取, 那么可以使用InputStreamReader(字节流,编码表)
• FileWriter是使用默认码表写出文件, 如果需要使用指定码表写出, 那么可以使用OutputStreamWriter(字节流,编码表)

• BufferedReader br =                                     //高效的用指定的编码表读
          new BufferedReader(new InputStreamReader(new FileInputStream("UTF-8.txt"), "UTF-8"));
  BufferedWriter bw =                                     //高效的用指定的编码表写
          new BufferedWriter(new OutputStreamWriter(new FileOutputStream("GBK.txt"), "GBK"));
  int ch;
  while((ch = br.read()) != -1) {
      bw.write(ch);
  }
  
  br.close();
  bw.close();