IO流的复习笔记

IO字节流和缓冲流

IO字节流的读取和写入

读取

 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;

 public class Test {
     public static void main(String[] args) {
         try (FileInputStream fis = new FileInputStream("java.txt")
         ) {
             byte[] bytes = new byte[40];
             int temp;
             while ((temp = fis.read(bytes)) != -1) {
                 System.out.println(new String(bytes, 0, temp));
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

写入

 import java.io.*;

 public class Test {
     public static void main(String[] args) {
         try (FileOutputStream fos = new FileOutputStream("file" + File.separator + "1024.txt", true) //写入时不清除原有数据
         ) {
             fos.write("Hello".getBytes());
             fos.write("\n".getBytes());  //换行
             fos.write("Wrold!".getBytes());
             fos.flush(); //刷新
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

IO字节流的文件拷贝

 import java.io.*;

 public class Test {
     public static void main(String[] args) {
         try (
                 FileOutputStream fos = new FileOutputStream("file" + File.separator + "new.txt");
                 FileInputStream fis = new FileInputStream("java.txt")
         ) {
             int temp;
             byte[] bytes = new byte[50];
             while ((temp = fis.read(bytes)) != -1) {
                 fos.write(bytes);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

IO缓冲流的读取和写入

 import java.io.*;

 /**
  * IO缓冲字节流的读取
  */
 public class Test {
     public static void main(String[] args) {
         try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream("java.txt"));
              BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "new.txt"));
         ) {
             int temp;
             while ((temp = bis.read()) != -1) {
                 bos.write(temp);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

IO字符流和缓冲流

IO字符流的文件拷贝

 import java.io.*;

 /**
  * IO字符流的文件拷贝
  */
 public class Test {
     public static void main(String[] args) {
         try (FileReader fr = new FileReader("java.txt");
              FileWriter fw = new FileWriter("file" + File.separator + "new.txt")
         ) {
             int temp;
             while ((temp = fr.read()) != -1) {
                 fw.write(temp);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

IO缓冲字符流的文件拷贝

 import java.io.*;

 /**
  * IO缓冲字符流的文件拷贝
  */
 public class Test {
     public static void main(String[] args) {
         try (
                 BufferedReader br = new BufferedReader(new FileReader("java.txt"));
                 BufferedWriter bw = new BufferedWriter(new FileWriter("file" + File.separator + "new.txt"))
         ) {
                 String msg;
                 while ((msg = br.readLine()) != null) {
                     bw.write(msg);
                     bw.newLine();  //换行
                     bw.flush();  //刷新
                 }

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

练习：图片简单的加密和解密

加密

 import java.io.*;

 /**
  * 图片的简单加密
  * 通过异或的方式
  */
 public class Test {
     public static void main(String[] args) {
         try (
                 BufferedInputStream bis = new BufferedInputStream(new FileInputStream("file" + File.separator + "123.jpg"));
                 BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "new123.jpg"))
         ) {
             int temp;
             while ((temp = bis.read()) != -1) {
                 bos.write(temp ^ 88);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

解密

 import java.io.*;

 /**
  * 图片的简单解密
  * 通过异或的方式
  */
 public class Test {
     public static void main(String[] args) {
         try (
                 BufferedInputStream bis = new BufferedInputStream(new FileInputStream("file" + File.separator + "code.jpg"));
                 BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "decode.jpg"))
         ) {
             int temp;
             while ((temp = bis.read()) != -1) {
                 bos.write(temp ^ 88);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }