Java IO——字符流

• 字符流
• 1)编码问题
• 2)认识文本和文本文件
•   java的文本(char)是16位无符号整数，是字符的unicode编码(双字节编码)
•   文件是byte byte byte.....的序列
•   文本文件是文本(char)序列按照某种编码方案(utf-8,utf-16be,gbk)序列化位byte的存储结果
• 3)字符流(Reader Writer)------>操作是文本、文本文件
•   字符的处理，一次处理一个字符
•   字符的底层仍然是基本的字节序列
•   字符流的基本实现
•   InputStreamReader  完成byte流解析为char流，按照编码解析
•   OutputStreamWriter 提供char流到byte流，按照编码处理
•   FileReader/Filewriter文件的读取和写入
•   BufferedReader/BufferedWriter
•   PrintlnWriter
•   BufferedWriter和PrintlnWriter的区别
•   BufferedWriter在写入时，不会自动换行，而PrintlnWriter会自动换行

• import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  
  public class IOUtil {
  	
  	public static void main(String[] args) throws IOException {
  		FileInputStream in = new FileInputStream("e://javaio//日记.txt");
  		InputStreamReader isr = new InputStreamReader(in,"gbk");//默认项目的编码
  		FileOutputStream out = new FileOutputStream("e://javaio//日记3.txt");
  		OutputStreamWriter osw = new OutputStreamWriter(out,"gbk");
  		/*int c;
  		while((c = isr.read()) != -1){
  			System.out.print((char)c);
  		}
  		*/
  		/**
  		 * 批量读取，放入buffer这个字符数组中，从第0个开始放置，最多放置buffer.length个
  		 * 返回的是读到的字符个数
  		 */
  		char[]  buffer = new char[8 * 1024];
  		int b;
  		while((b = isr.read(buffer, 0, buffer.length)) != -1){
  			String s = new String(buffer,0,b);
  			System.out.print(s);
  			osw.write(buffer,0,b);
  			osw.flush();
  		}
  		isr.close();
  		osw.close();
  		in.close();
  		out.close();
  	}
  
  }
             

  import java.io.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  
  public class BrAndBf {
  
  	public static void main(String[] args) throws IOException {
  		// 对文件进行读写操作
  		BufferedReader br = new BufferedReader(
  				new InputStreamReader(
  						new FileInputStream("e:\\javaio\\日记.txt")));
  		BufferedWriter bw = new BufferedWriter(
  				new OutputStreamWriter(
  						new FileOutputStream("e:\\javaio\\日记5.txt")));
  		PrintWriter pw = new PrintWriter("e:\\javaio\\日记6.txt");
  		String line;
  		while((line = br.readLine()) != null){
  			System.out.println(line);//一次读一行，并不能识别换行
  			bw.write(line);
  			//单独写出换行操作
  			bw.newLine();
  			bw.flush();
  			pw.println(line);
  			pw.flush();
  			
  		}
  		br.close();
  		bw.close();
  		pw.close();
  	}
  }
             

  import java.io.FileReader;
  import java.io.FileWriter;
  import java.io.IOException;
  
  public class FrAndFwDemo {
  
  	public static void main(String[] args) throws IOException {
  		FileReader fr = new FileReader("e:\\javaio\\日记.txt");
  		FileWriter fw = new FileWriter("e:\\javaio\\日记4.txt");
  		char[] buffer = new char[2 * 1024];
  		int c;
  		while((c = fr.read(buffer,0,buffer.length))!= -1){
  			fw.write(buffer,0,c);
  			fw.flush();
  		}
  		fr.close();
  		fw.close();
  	}
  
  }