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[Java教程]Java输入/输出流体系


在用java的io流读写文件时,总是被它的各种流能得很混乱,有40多个类,理清啦,过一段时间又混乱啦,决定整理一下!以防再忘

Java输入/输出流体系

1.字节流和字符流

字节流:按字节读取。字符流:按字符读取。

字符流读取方便,字节流功能强大,当不能用字符流时,可以用字节流。

字节流基类:InputStream、OutputStream

 InputStream方法:

 

OutputStream方法:

 

字符流基类:Reader、Writer

Reader方法:

 

Writer方法:

 

2.输入输出流体系

 

3.转换流

InputStreamReader:字节输入流->字符输入流的转换

OutputStreamWriter:字节输出流->字符输出流的转换

例如:字节输入流->字符输入流的转换

字节流使用不方便,而普通的Reader读取也不太方便,转换成BufferReader,利用BufferReader的readLine(),一次读取一行。

BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));        String result = "";        String line = "";        while((line = reader.readLine())!= null){          result = result+ line;        }        System.out.println(result);

InputStream to String:

private static String changeInputeStream(InputStream inputStream,String encode) {    //通常叫做内存流,写在内存中的    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();    byte[] data = new byte[1024];    int len = 0;    String result = "";    if(inputStream != null){      try {        while((len = inputStream.read(data))!=-1){          outputStream.write(data, 0, len);        }        //result是在服务器端设置的doPost函数中的        result = new String(outputStream.toByteArray(),encode);        outputStream.flush();        outputStream.close();        inputStream.close();      } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();      }    }    return result;  }

 

InputStream->StringBuffer:

StringBuffer buffer = new StringBuffer();    InputStreamReader reader =new InputStreamReader(request.getInputStream(),"utf-8");    char[] requestchar = new char[5];    if(reader != null){      System.out.println("默认编码:"+reader.getEncoding());//默认编码:UTF8    }    //buffer reader.readLine()    while((temp = reader.read(requestchar))!=-1){      buffer.append(requestchar, 0, temp);      System.out.println(buffer.toString());    }    String result = buffer.toString();

4.文件读写:

class Kaoshi{public static void main(String[] args){ Scanner in=new Scanner(System.in); int score=0;              //分数; StringBuffer answer=new StringBuffer();//存放用户答案,动态字符串; String result="ACDD";         //正确答案;try{                     FileReader file=new FileReader("Test.txt");   //打开文件; BufferedReader intw=new BufferedReader(file);  //缓冲流,按行读; String s=null;             while((s=intw.readLine())!=null){       //判断不为空;  if(!s.startsWith("*")){              System.out.println(s);   }  else{    System.out.println("请输入正确答案:");     String str=in.next();     char c= str.charAt(0);//收集答案;     answer.append(c);  } }       }catch(IOException e){   e.printStackTrace(); }  for(int i=0;i<result.length();i++){   if(result.charAt(i)==answer.charAt(i)||     result.charAt(i)==answer.charAt(i)-32){    score+=25;   } } System.out.println(score);} }