Problems and solutions in the learning process of file class

1.  utilize File Constructors ,new  A file directory file
1) Create multiple files and directories in it , Test what you have learned File Class method 
2) Write the method manually , Implementation delete file Operation of the specified file in 
​
2.  Determine whether there is a suffix named .jpg The file of , If there is , Just output the file name 
​
3.  Traverse the specified directory all file names , Include files in the subdirectory （ Pay attention to this sentence , Classical recursive method , If you don't know the way of thinking, ask directly ）.
​
4.  Create a and a.txt The file is another file in the same directory b.txt
​
5. operation D On the plate my.txt file 
1)   Judge my.txt Does the file exist 
2)   Delete if present ; Created if it does not exist 
​
6.File What is the function of class ? Is it a flow ?
​
7. Use File Class to delete a folder （ for example D On the plate temp Folder ） All the files and folders under :
1）   Judge temp File type under folder , If it is a file, delete it directly 
2）   If it is a folder, get the sub files and folders under the folder 
3）   Use recursion to delete all temp Files and folders under folders （ May refer to 3 topic ）

1.  utilize File Constructors ,new  A file directory file
1) Create multiple files and directories in it , Test what you have learned File Class method 
2) Write the method manually , Implementation delete file Operation of the specified file in */
1.1 Code ：
package com.B.IOStream_14.FileDemo.Ask;
​
import java.io.File;
import java.io.IOException;
​
public class FileA1 {
    public static void main(String[] args) throws IOException {
// Create objects   、 file 
        File f1 = new File("E:\\JavaDemo\\Demo03\\Web");
        System.out.println(f1.mkdirs()); // Create multi-level directory 
        File f2 = new File("E:\\JavaDemo\\Demo04");
        System.out.println(f2.mkdir()); // Create a single level directory 
        File f3 = new File("E:\\JavaDemo\\Demo04\\ Today Friday is very happy .txt");
        System.out.println(f3.createNewFile());  // create a file 
        File f4 = new File("E:\\JavaDemo\\Demo04\\ Tomorrow and Saturday will be happier .txt");
        System.out.println(f4.createNewFile());  // create a file 
         File f5 = new File("E:\\JavaDemo\\Demo04\\ Happy Sunday the day after tomorrow .txt");
        System.out.println(f5.createNewFile());  // create a file 
        System.out.println("-----------");
​
//       Delete file f5
        f5.delete();
​
        // Create a... Based on the given path File object 
        File file = new File("E:\\JavaDemo");
// Calling method 
        textFile(file);
//         Output file path 
        System.out.println(file);
    }
​
    //         Compiling method , Implementation delete file Operation of the specified file in 
    public static void textFile(File file) {
//        file The files in the object are stored in File File array 
        File[] fileArrary = file.listFiles();
        if (fileArrary != null) { // Add a judgment statement that is not empty , Increase robustness 
            for (File f : fileArrary) {  // enhance for Cyclic ergodic set , first for Delete content 
                // Determine whether the file is a file directory   It's recursion   No delete 
                if (f.isDirectory()) {
                    // yes ： Recursively call 
                    textFile(f);
                } else
                    // No ： Get the absolute path output on the console 
                    System.out.println(f.getAbsoluteFile());
            }
        }
​
​
    }
}

 Run the following ：

  The runtime found that other files could not be output ,debug During debugging, these contents appear but are not output ,

create a file ：

  Delete file ：

1. Determine whether there is a suffix named .jpg The file of , If there is , Just output the file name

   Code ：

   package com.B.IOStream_14.FileDemo.Ask;
   ​
   import java.io.File;
   import java.io.IOException;
   ​
   //2.  Determine whether there is a suffix named .jpg The file of , If there is , Just output the file name 
   public class FileA2 {
       public static void main(String[] args) throws IOException {
           //1. Create a path where the current file is located 
           File file = new File("E:\\JavaDemo\\Demo04");
   ​
           File f1 = new File("E:\\JavaDemo\\Demo04\\ I'm so happy to buy a big orange dress .txt");
           System.out.println(f1.createNewFile());  // create a file 
           File f2 = new File("E:\\JavaDemo\\Demo04\\ No money. QAQ.txt");
           System.out.println(f2.createNewFile());  // create a file 
           File f3 = new File("E:\\JavaDemo\\Demo04\\ Mura baby .jpg");
           System.out.println(f3.createNewFile());  // create a file 
   ​
           //2. Store the file name in the current directory into the character array 
           String[] fileNames = file.list();
           for (String fileName : fileNames) {
               //Java endsWith()  Method 
               if (fileName.endsWith(".jpg")) {
                   System.out.println(fileName);
               }
           }
   //endsWith()  Method to test whether the string ends with the specified suffix .
   // grammar 
   //public boolean endsWith(String suffix)
   // Parameters 
   //suffix --  Specified suffix .
   // Return value 
   // If the character sequence represented by the parameter is the suffix of the character sequence represented by this object , Then return to  true; Otherwise return to  false. Be careful , If the argument is an empty string , Or equal to this  String  object （ use  equals(Object)  Method determination ）, The result is  true.
   ​
   ​
       }
   }

   expand ：

   Introduced JavaendsWith() Method

   ---

   endsWith() Method to test whether the string ends with the specified suffix .

   grammar

   public boolean endsWith(String suffix)

   Parameters

   • suffix -- Specified suffix .

   • Such as ：

     for (String fileName : fileNames) {
         //Java endsWith()  Method 
         if (fileName.endsWith(".jpg")) {
             System.out.println(fileName);
         }
     }

   Return value

   If the character sequence represented by the parameter is the suffix of the character sequence represented by this object , Then return to true; Otherwise return to false. Be careful , If the argument is an empty string , Or equal to this String object （ use equals(Object) Method determination ）, The result is true.

   function ：

   

    

   1. Traverse the specified directory all file names , Include files in the subdirectory （ Pay attention to this sentence , Classical recursive method , If you don't know the way of thinking, ask directly ）.

      Code ：

      package com.B.IOStream_14.FileDemo.Ask;
      ​
      import java.io.File;
      import java.io.IOException;
      //3. Traverse the specified directory all file names , Include files in the subdirectory （ Pay attention to this sentence , Classical recursive method ）
      public class FileA3 {
          public static void main(String[] args) throws IOException {
              //1. Create a path where the current file is located 
              File file = new File("E:\\JavaDemo");
      // Calling method 
                  textFile(file);
                  System.out.println(file);
              }
      ​
              //         Compiling method , Implementation delete file Operation of the specified file in 
              public static void textFile(File file) {
      //        file The files in the object are stored in File File array 
                  File[] fileArrary = file.listFiles();
                  if (fileArrary != null) { // Add a judgment statement that is not empty , Increase robustness 
                      for (File f : fileArrary) {  // enhance for Cyclic ergodic set , first for Delete content 
                          // Determine whether the file is a file directory   It's recursion   No delete 
                          if (f.isDirectory()) {
                              // yes ： Recursively call 
                              textFile(f);
                          } else
                              // No ： Get the absolute path output on the console 
                              System.out.println(f.getAbsoluteFile());
                      }
                  }
      ​
              }
      }

   function ：

    

2. 6.File What is the function of class ? Is it a flow ?

   File Class is used to implement java Classes that interact with file data , It's not flow .

   7. Use File Class to delete a folder （ for example D On the plate temp Folder ） All the files and folders under : 1） Judge temp File type under folder , If it is a file, delete it directly 2） If it is a folder, get the sub files and folders under the folder 3） Use recursion to delete all temp Files and folders under folders （ May refer to 3 topic ）

package com.B.IOStream_14.FileDemo.Ask;
​
import java.io.File;
import java.io.IOException;
​
//7. Use File Class to delete a folder （ for example D On the plate temp Folder ） All the files and folders under :
//1）    Judge temp File type under folder , If it is a file, delete it directly 
//2）    If it is a folder, get the sub files and folders under the folder 
//3）    Use recursion to delete all temp Files and folders under folders （ May refer to 3 topic ）
public class FileA7 {
    public static void main(String[] args) throws IOException {
        //1. Create a path where the current file is located 
        File file = new File("D:\\temp");
        System.out.println(file.mkdir());
//         create a file 
        File f3 = new File("D:\\temp\\ Today Friday is very happy .txt");
        System.out.println(f3.createNewFile());  // create a file 
        File f4 = new File("D:\\temp\\ Tomorrow and Saturday will be happier .txt");
        System.out.println(f4.createNewFile());  // create a file 
        File f5 = new File("D:\\temp\\ Happy Sunday the day after tomorrow .txt");
        System.out.println(f5.createNewFile());  // create a file 
        System.out.println("-----------");
// Calling method 
        textFile(file);
        System.out.println(file);
        System.out.println("-----------");
​
​
        file.delete();
        System.out.println(file);
    }
​
    //         Compiling method , Implementation delete file Operation of the specified file in 
    public static void textFile(File file) {
//        file The files in the object are stored in File File array 
        File[] fileArrary = file.listFiles();
        if (fileArrary != null) { // Add a judgment statement that is not empty , Increase robustness 
            for (File f : fileArrary) {  // enhance for Cyclic ergodic set , first for Delete content 
                // Determine whether the file is a file directory   It's recursion   No delete 
                if (f.isDirectory()) {
                    // yes ： Recursively call 
                    textFile(f);
                } else
                    // No ： Get the absolute path output on the console 
                    System.out.println(f.getAbsoluteFile());
            }
        }
​
    }
}

Create file directory temp And the content of the document ：

Execute delete and print ：