Filter, FilenameFilter用法和文件排序

Filter, FilenameFilter用法和文件排序
FileFilter和FilenameFilter这两个类的用法都很简单，都只有一个方法

FileFilter
/**
* @param pathname The abstract pathname to be tested
*/
boolean accept(File pathname)
用法示例：
import java.io.File;
import java.io.FileFilter;

public class Main {

  public static void main(String[] args) {

    File cwd = new File(System.getProperty("user.dir"));
    File[] htmlFiles = cwd.listFiles(new HTMLFileFilter());
    for (int i = 0; i < htmlFiles.length; i++) {
      System.out.println(htmlFiles[i]);
    }
  }
}

class HTMLFileFilter implements FileFilter {

  public boolean accept(File pathname) {

    if (pathname.getName().endsWith(".html"))
      return true;
    if (pathname.getName().endsWith(".htm"))
      return true;
    return false;
  }
}

FilenameFilter

/**
* @param dir - the directory in which the file was found.
* @param name - the name of the file.
*/
boolean accept(File dir,  String name)

用法示例：
import java.io.File;
import java.io.FilenameFilter;

class ExtensionFilter implements FilenameFilter {
  String ext;

  public ExtensionFilter(String ext) {
    this.ext = "." + ext;
  }

  public boolean accept(File dir, String name) {
    return name.endsWith(ext);
  }
}

public class Main {
  public static void main(String args[]) {
    String dirname = "/java";
    File f1 = new File(dirname);
    FilenameFilter only = new ExtensionFilter("html");
    String s[] = f1.list(only);
    for (int i = 0; i < s.length; i++) {
      System.out.println(s[i]);
    }
  }
}

文件排序
排序规则：目录排在前面，按字母顺序排序文件列表

List<File> files = Arrays.asList(new File("<目录>").listFiles());
Collections.sort(files, new Comparator<File>(){
    @Override
    public int compare(File o1, File o2) {
    if(o1.isDirectory() && o2.isFile())
        return -1;
    if(o1.isFile() && o2.isDirectory())
            return 1;
    return o1.getName().compareTo(o2.getName());
    }
});

for(File f : files)
    System.out.println(f.getName());

from: www.hilyb.com