Recursively looping into directories and subdirectories to get files that matching with pattern

1. import java.io.File;
2. import java.util.ArrayList;
3. import java.util.List;
4. import java.util.regex.*;
6. public class TechFact555FileMatching {
7.   // Pattern to match with file name
8.   public static final String FILE_PATTERN = "[a-zA-Z0-9]{6}";
9.  
10.   public static void main(String[] args) {
11.     List<File> resultFiles = new ArrayList<>();
12.     TechFact555FileMatching fileMatching = new TechFact555FileMatching();
13.     
14.     // Specify parent folder to fetch files
15.     fileMatching.listFiles(new File("E:/folder"), resultFiles);
16.    
17.     for (File resultFile : resultFiles) {
18.       System.out.print(resultFile.getName());
19.     }
20.   }
21.  
22.   // Recursively looping into folders to get Files
23.   void listFiles(File directory, List<File> filesList) {
24.     File[] filesAndFoldersList = directory.listFiles();
25.     if (filesAndFoldersList != null) {
26.       for (File fileOrFolder : filesAndFoldersList) {
27.         if (fileOrFolder.isDirectory()) {
28.           listFiles(fileOrFolder, filesList);
29.         } else if (fileOrFolder.isFile() && Pattern.matches(FILE_PATTERN, fileOrFolder.getName())) {
30.           filesList.add(fileOrFolder);
31.         }
32.       }
33.     }
34.   }
35. }

Pass the Directory to fetch files as first parameter and list of files to add the pattern matching pattern as second parameter into listFiles function.

Java program to handle arithmetic [Calculator] with Exception using Scanner

1. import java.util.Scanner;
2. import java.io.*;
3. 
   
4. public class TechFact555Calculator {
5.     public static void main(String[] args) {
6.         Scanner reader = new Scanner(System.in);
7.         System.out.print("Enter two numbers: ");
8.         
9.         // nextDouble() reads the next double from the keyboard
10.         double first = reader.nextDouble();
11.         double second = reader.nextDouble();
12.         System.out.print("Enter an operator (+, -, *, /): ");
13. 
    
14.         char operator = reader.next().charAt(0);
15.         double result;
16.         try {
17.             switch(operator){
18. 
    
19.             case '+':
20.                 result = first + second;
21.                 break;
22. 
    
23.             case '-':
24.                 result = first - second;
25.                 break;
26. 
    
27.             case '*':
28.                 result = first * second;
29.                 break;
30. 
    
31.             case '/':
32.                 result = first / second;
33.                 break;
34. 
                // operator doesn't match any case constant (+, -, *, /)
35.             default:
36.                 System.out.printf("Error! operator is not correct");
37.                 return;
38.             }
39.             System.out.printf("%.1f %c %.1f = %.1f", first, operator, second, result);
40.         } catch(Exception e) {
41.             System.out.print("Exception occurred " + e);
42.         }
43.     }
44. }
45. 
    

Get token value from request header in java

1. public class TechFact555 {
2.  public String getHeader(HttpServletRequest request) {
3.    String token = request.getHeader("header-key");
4.    // Validate token string
5.     return token;
6.   }
7. }

To get value in request, use HttpServletRequest object with exact key.

• NOTE: Header key is case-sensitive.