How to Efficiently Find Files Using Wildcard Patterns in Java?

Finding Files with Wildcard Strings in Java

Finding files matching a specific wildcard pattern is a common task in Java. To address this need, Apache commons-io provides the FileUtils class with methods like listFiles and iterateFiles.

Suppose you have a wildcard pattern like this:

../Test?/sample*.txt

To list matching files using FileUtils:

File dir = new File(".");
FileFilter fileFilter = new WildcardFileFilter("sample*.java");
File[] files = dir.listFiles(fileFilter);

for (File file : files) {
    System.out.println(file);
}

This code iterates over the files in the current directory that match the specified wildcard. However, to handle nested directories (e.g. TestX folders), you can iterate through the directories first:

File[] dirs = new File(".").listFiles(new WildcardFileFilter("Test*.java"));

for (File dir : dirs) {
    if (dir.isDirectory()) {
        File[] files = dir.listFiles(new WildcardFileFilter("sample*.java"));
    }
}

While this solution is effective, it may not be as efficient as desired. Consider using a RegexFileFilter for more flexible and complex matching criteria.

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