src/FrameBusCollection.java

@@ -17,23 +17,6 @@ import java.io.FileNotFoundException;
 import java.io.FileWriter;
 import java.io.IOException;
 
-class TxtSaveFilter extends FileFilter {
-    @Override
-    public boolean accept(File f) {
-        if (f.isDirectory()) {
-            return false;
-        }
-
-        String s = f.getName().toLowerCase();
-
-        return s.endsWith(".txt");
-    }
-
-    @Override
-    public String getDescription() {
-        return "*.txt";
-    }
-}
 public class FrameBusCollection extends JFrame {
     private BusesGenericStorage storage;
     private JList<String> listBoxStorages;

src/TxtSaveFilter.java

@@ -0,0 +1,20 @@
+import javax.swing.filechooser.FileFilter;
+import java.io.File;
+
+public class TxtSaveFilter extends FileFilter {
+    @Override
+    public boolean accept(File f) {
+        if (f.isDirectory()) {
+            return false;
+        }
+
+        String s = f.getName().toLowerCase();
+
+        return s.endsWith(".txt");
+    }
+
+    @Override
+    public String getDescription() {
+        return "*.txt";
+    }
+}