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

 1 import java.io.FileInputStream;
 2 import java.io.FileNotFoundException;
 3 import java.io.IOException;
 4 
 5 public class Test {
 6     public static void main(String[] args) {
 7         try (FileInputStream fis = new FileInputStream("java.txt")
 8         ) {
 9             byte[] bytes = new byte[40];
10             int temp;
11             while ((temp = fis.read(bytes)) != -1) {
12                 System.out.println(new String(bytes, 0, temp));
13             }
14         } catch (FileNotFoundException e) {
15             e.printStackTrace();
16         } catch (IOException e) {
17             e.printStackTrace();
18         }
19     }
20 }

写入

 1 import java.io.*;
 2 
 3 public class Test {
 4     public static void main(String[] args) {
 5         try (FileOutputStream fos = new FileOutputStream("file" + File.separator + "1024.txt", true) //写入时不清除原有数据
 6         ) {
 7             fos.write("Hello".getBytes());
 8             fos.write("
".getBytes());  //换行
 9             fos.write("Wrold!".getBytes());
10             fos.flush(); //刷新
11         } catch (FileNotFoundException e) {
12             e.printStackTrace();
13         } catch (IOException e) {
14             e.printStackTrace();
15         }
16     }
17 }

IO字节流的文件拷贝

 1 import java.io.*;
 2 
 3 public class Test {
 4     public static void main(String[] args) {
 5         try (
 6                 FileOutputStream fos = new FileOutputStream("file" + File.separator + "new.txt");
 7                 FileInputStream fis = new FileInputStream("java.txt")
 8         ) {
 9             int temp;
10             byte[] bytes = new byte[50];
11             while ((temp = fis.read(bytes)) != -1) {
12                 fos.write(bytes);
13             }
14         } catch (FileNotFoundException e) {
15             e.printStackTrace();
16         } catch (IOException e) {
17             e.printStackTrace();
18         }
19     }
20 }

IO缓冲流的读取和写入

 1 import java.io.*;
 2 
 3 /**
 4  * IO缓冲字节流的读取
 5  */
 6 public class Test {
 7     public static void main(String[] args) {
 8         try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream("java.txt"));
 9              BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "new.txt"));
10         ) {
11             int temp;
12             while ((temp = bis.read()) != -1) {
13                 bos.write(temp);
14             }
15         } catch (FileNotFoundException e) {
16             e.printStackTrace();
17         } catch (IOException e) {
18             e.printStackTrace();
19         }
20     }
21 }

IO字符流和缓冲流

IO字符流的文件拷贝

 1 import java.io.*;
 2 
 3 /**
 4  * IO字符流的文件拷贝
 5  */
 6 public class Test {
 7     public static void main(String[] args) {
 8         try (FileReader fr = new FileReader("java.txt");
 9              FileWriter fw = new FileWriter("file" + File.separator + "new.txt")
10         ) {
11             int temp;
12             while ((temp = fr.read()) != -1) {
13                 fw.write(temp);
14             }
15         } catch (FileNotFoundException e) {
16             e.printStackTrace();
17         } catch (IOException e) {
18             e.printStackTrace();
19         }
20     }
21 }

IO缓冲字符流的文件拷贝

 1 import java.io.*;
 2 
 3 /**
 4  * IO缓冲字符流的文件拷贝
 5  */
 6 public class Test {
 7     public static void main(String[] args) {
 8         try (
 9                 BufferedReader br = new BufferedReader(new FileReader("java.txt"));
10                 BufferedWriter bw = new BufferedWriter(new FileWriter("file" + File.separator + "new.txt"))
11         ) {
12                 String msg;
13                 while ((msg = br.readLine()) != null) {
14                     bw.write(msg);
15                     bw.newLine();  //换行
16                     bw.flush();  //刷新
17                 }
18 
19         } catch (FileNotFoundException e) {
20             e.printStackTrace();
21         } catch (IOException e) {
22             e.printStackTrace();
23         }
24     }
25 }

练习：图片简单的加密和解密

加密

 1 import java.io.*;
 2 
 3 /**
 4  * 图片的简单加密
 5  * 通过异或的方式
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         try (
10                 BufferedInputStream bis = new BufferedInputStream(new FileInputStream("file" + File.separator + "123.jpg"));
11                 BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "new123.jpg"))
12         ) {
13             int temp;
14             while ((temp = bis.read()) != -1) {
15                 bos.write(temp ^ 88);
16             }
17         } catch (FileNotFoundException e) {
18             e.printStackTrace();
19         } catch (IOException e) {
20             e.printStackTrace();
21         }
22     }
23 }

解密

 1 import java.io.*;
 2 
 3 /**
 4  * 图片的简单解密
 5  * 通过异或的方式
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         try (
10                 BufferedInputStream bis = new BufferedInputStream(new FileInputStream("file" + File.separator + "code.jpg"));
11                 BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "decode.jpg"))
12         ) {
13             int temp;
14             while ((temp = bis.read()) != -1) {
15                 bos.write(temp ^ 88);
16             }
17         } catch (FileNotFoundException e) {
18             e.printStackTrace();
19         } catch (IOException e) {
20             e.printStackTrace();
21         }
22     }
23 }