如何检查Java中是否存在带通配符的文件？

Question

我有一个目录,里面是文件命名"a_id_XXX.zip".

如何检查文件是否存在给定id和File dir？

Answer 1

将FileFilter(匿名编码)传递给listFiles()dir 的方法File,如下所示:

File dir = new File("some/path/to/dir");
final String id = "XXX"; // needs to be final so the anonymous class can use it
File[] matchingFiles = dir.listFiles(new FileFilter() {
    public boolean accept(File pathname) {
        return pathname.getName().equals("a_id_" + id + ".zip");
    }
});

捆绑为方法,它看起来像:

public static File[] findFilesForId(File dir, final String id) {
    return dir.listFiles(new FileFilter() {
        public boolean accept(File pathname) {
            return pathname.getName().equals("a_id_" + id + ".zip");
        }
    });
}

你可以称之为:

File[] matchingFiles = findFilesForId(new File("some/path/to/dir"), "XXX");

或者只是检查是否存在,

boolean exists = findFilesForId(new File("some/path/to/dir"), "XXX").length > 0

Answer 2

我创建了以a_id_123.zip,a_id_124.zip,a_id_125.zip,a_id_126.zip命名的zip文件,看起来工作正常,但我不确定它是否适合您.如果存在上面列出的文件,则输出如下

• 找到了a_id_123.zip
• 找到了a_id_124.zip
• 找到了a_id_125.zip

• 找到了a_id_126.zip

  public static void main(String[] args) {
  
      String pathToScan = ".";
      String fileThatYouWantToFilter;
      File folderToScan = new File(pathToScan); // import -> import java.io.File;
      File[] listOfFiles = folderToScan.listFiles();
  
      for (int i = 0; i < listOfFiles.length; i++) {
  
          if (listOfFiles[i].isFile()) {
              fileThatYouWantToFilter = listOfFiles[i].getName();
              if (fileThatYouWantToFilter.startsWith("a_id_")
                      && fileThatYouWantToFilter.endsWith(".zip")) {
                  System.out.println("found" + " " + fileThatYouWantToFilter);
              }
          }
      }
  }
  

Answer 3

该解决方案概括了 Bohemian 的答案。它使用正则表达式，并用 Java 8 lambda 表达式替换内部类。感谢@Bohemian 最初的实现。

import java.io.File;

public class FileFinder {
    public static void main(String[] args){
        File directory = new File("D:\\tmp");
        String id = "20140430104033";
        for (File f : findFilenamesWithId(id, directory)){
            System.out.println(f.getAbsoluteFile());
        }
    }

    /** Finds files in the specified directory whose names are formatted 
        as "a_id_ID.zip" */
    public static File[] findFilenamesWithId(String ID, File dir) {
        return findFilenamesMatchingRegex("^a_id_" + ID + "\\.zip$", dir);
    }

    /** Finds files in the specified directory whose names match regex */
    public static File[] findFilenamesMatchingRegex(String regex, File dir) {
        return dir.listFiles(file -> file.getName().matches(regex));
    }
}