java文件IO总结

╰+攻爆jí腚メ 2022-06-12 12:16 130阅读 0赞

![这里写图片描述][SouthEast]

## 一.字节流 ##

import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    
    public class CopyByByteStream {
    
        public static void main(String[] args) {
            try {
    
                FileInputStream fis = new FileInputStream("movie.mp4");
                FileOutputStream fos = new FileOutputStream("movie_new.mp4");
    
                byte input[] = new byte[50];
                long before = System.currentTimeMillis();
                int count = 0;
                while (fis.read(input) != -1) {
                    fos.write(input);
                    count++;
                }
                fos.flush();
                fis.close();
                fos.close();
                System.out.println(System.currentTimeMillis()-before+"ms");
                System.out.println("done");
                System.out.println("读取了："+count+"次");
    
    
    
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
    }

## 二.字符流 ##

import java.io.*;
    
    public class CopyFile {
       public static void main(String args[]) throws IOException
       {
          FileReader in = null;
          FileWriter out = null;
          try {
             in = new FileReader("input.txt");
             out = new FileWriter("output.txt");
             int c;
             while ((c = in.read()) != -1) {
                out.write(c);
             }
          }finally {
             if (in != null) {
                in.close();
             }
             if (out != null) {
                out.close();
             }
          }
       }
    
    
    public class RWByCharStream {
        public static void main(String[] args) {
            try {
                //File file = new File("java.txt");
                FileInputStream fis = new FileInputStream("java.txt");
                FileOutputStream fos = new FileOutputStream("java_new.txt");
                InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
                OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");
                char input[] = new char[100];
                int l = 0;
                while ((l = isr.read(input)) != -1) {
                    //String inputString = new String(input,0,l);
                    osw.write(input,0,l);
                }
                isr.close();
                fis.close();
                osw.close();
                fos.close();
                System.out.println("done");
    
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

**包装为BufferedReader更方便：**

import java.io.BufferedInputStream;
    import java.io.BufferedOutputStream;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.IOException;
    public class ReadByBufferedByteStream { 
        public static void main(String[] args) {
            try {
                FileInputStream fis = new FileInputStream("movie.mp4");
                BufferedInputStream bis = new BufferedInputStream(fis,1000000);
                FileOutputStream fos = new FileOutputStream("moive_new.mp4");
                BufferedOutputStream bos = new BufferedOutputStream(fos,1000000);
                //大型文件对应的数组可以大一些，小文件对应的数组小一些
                byte input[] = new byte[100000];
                int count = 0;
                long before = System.currentTimeMillis();
                while (bis.read(input) != -1) {
                    bos.write(input);
                    count++;
                }
                bos.flush();
                bis.close();
                fis.close();
                bos.close();
                fos.close();
                System.out.println(System.currentTimeMillis()-before+"ms");
                System.out.println("读取了："+count+"次");
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

## 三.标准流 ##

import java.io.*;
    
    public class ReadConsole {
       public static void main(String args[]) throws IOException
       {
          InputStreamReader cin = null;
          try {
             cin = new InputStreamReader(System.in);
             System.out.println("Enter characters, 'q' to quit.");
             char c;
             do {
                c = (char) cin.read();
                System.out.print(c);
             } while(c != 'q');
          }finally {
             if (cin != null) {
                cin.close();
             }
          }
       }
    }

## 四.文件输入输出流 ##

import java.io.*;
    
    public class fileStreamTest{
    
       public static void main(String args[]){
       try{
          byte bWrite [] = {
       11,21,3,40,5};
          OutputStream os = new FileOutputStream("test.txt");
          for(int x=0; x < bWrite.length ; x++){
             os.write( bWrite[x] ); // writes the bytes
          }
          os.close();
          InputStream is = new FileInputStream("test.txt");
          int size = is.available();
          for(int i=0; i< size; i++){
             System.out.print((char)is.read() + " ");
          }
          is.close();
       }catch(IOException e){
          System.out.print("Exception");
       }    
       }
    }

**输出文本都应使用处理流PrintWriter**

[SouthEast]: /images/20220612/1a4b9f851553483488dec5b466ddfca0.png