Files.java

package au.gov.amsa.util;

import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.regex.Pattern;

public final class Files {

    private static Comparator<File> FILE_COMPARATOR = (a, b) -> a.getAbsolutePath().compareTo(
            b.getAbsolutePath());

    public static List<File> find(File file, final Pattern pattern) {
        return find(file, pattern, true);
    }

    public static List<File> find(File file, final Pattern pattern, boolean sort) {
        if (!file.exists())
            return Collections.emptyList();
        else {
            if (!file.isDirectory() && pattern.matcher(file.getName()).matches())
                return Collections.singletonList(file);
            else if (file.isDirectory()) {
                List<File> list = new ArrayList<File>();
                File[] files = file.listFiles();
                if (files != null)
                    for (File f : file.listFiles()) {
                        if (!f.getName().startsWith(".")) {
                            if (f.isFile() && pattern.matcher(f.getName()).matches())
                                list.add(f);
                            else
                                list.addAll(find(f, pattern, sort));
                        }
                    }
                Collections.sort(list, FILE_COMPARATOR);
                return list;
            } else
                return Collections.emptyList();
        }
    }
}