Jagepard / JavaDesignPatterns-Interpreter

public class Interpreter implements InterpreterInterface {

    private final List<AlbumInterface> registry = new ArrayList<>();

    @Override

    public String interpret(String input) {

        String[] exploded = input.split(" ");

        for (String value : exploded) {

            if (this.isNumeric(value)) {

                int number = Integer.parseInt(value) - 1;

                return this.getDataFromRegistry(exploded, this.registry.get(number));

            }

        }

        return input;

    }

    public void addAlbumToRegistry(AlbumInterface album) {

        this.registry.add(album);

    }

    private boolean isNumeric(String str) {

        return str != null && str.matches("[-+]?\\d*\\.?\\d+");

    }

    private String getDataFromRegistry(String[] exploded, AlbumInterface item)

    {

        StringBuilder output = new StringBuilder();

        for (String value : exploded) {

            if (value.equals("album")) output.append(item.getName()).append(" ");

            if (value.equals("author")) output.append(item.getAuthor()).append(" ");

        }

        return output.toString();