How Can I Efficiently Find Files Matching Wildcard Patterns in Java?

Finding Files with Wildcard Patterns in Java

Identifying files matching a specific wildcard pattern can be daunting in Java. To tackle this challenge, consider the following approaches:

Using org.apache.commons.io.filefilter.WildcardFileFilter

• Create a FileFilter instance using WildcardFileFilter:

  FileFilter fileFilter = new WildcardFileFilter("sample*.txt");

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• Apply the filter to a directory to list matching files:

  File dir = new File(".");
  File[] files = dir.listFiles(fileFilter);

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Handling Relative Paths

To account for relative paths in directories:

• Iterate Through Subdirectories:

  FileFilter dirFilter = new WildcardFileFilter("Test*");
  File[] subdirs = new File(".").listFiles(dirFilter);
  for (File subdir : subdirs) {
    if (subdir.isDirectory()) {
      File[] files = subdir.listFiles(fileFilter);
    }
  }

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• Use Recursion:

  File current = ...; // start at any directory
  File[] files = new ArrayList<>();
  processFiles(files, current, fileFilter);
  
  private void processFiles(List<File> files, File dir, FileFilter filter) {
    File[] subdirs = dir.listFiles(dirFilter);
    for (File subdir : subdirs) {
      if (subdir.isDirectory()) {
        processFiles(files, subdir, filter);
      }
      else if (filter.accept(subdir)) {
        files.add(subdir);
      }
    }
  }

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Alternative Approaches

• RegexFileFilter: This filter uses regular expressions to match file patterns, but may be more complex to use.
• Custom Implementation: Create a custom class implementing the FileFilter interface to handle wildcard matching.

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