add FilenameRegexFilter

src/main/java/org/cobbzilla/util/io/FilenameRegexFilter.java

@@ -0,0 +1,18 @@
+package org.cobbzilla.util.io;
+
+import lombok.AllArgsConstructor;
+
+import java.io.File;
+import java.io.FilenameFilter;
+import java.util.regex.Pattern;
+
+@AllArgsConstructor
+public class FilenameRegexFilter implements FilenameFilter {
+
+    private final Pattern pattern;
+
+    public FilenameRegexFilter (String p) { pattern = Pattern.compile(p); }
+
+    @Override public boolean accept(File dir, String name) { return pattern.matcher(name).matches(); }
+
+}