Java Language
Enum, начиная с номера

Вступление

Enum с именем при начале

public enum BookCode {
    _10A("Simon Haykin", "Communication System"),
    _42B("Stefan Hakins", "A Brief History of Time"),
    E1("Sedra Smith", "Electronics Circuits");

    private String author;
    private String title;

    BookCode(String author, String title) {
        this.author = author;
        this.title = title;
    }

    public String getName() {
        String name = name();
        if (name.charAt(0) == '_') {
            name = name.substring(1, name.length());
        }
        return name;
    }

    public static BookCode of(String code) {
        if (Character.isDigit(code.charAt(0))) {
            code = "_" + code;
        }
        return BookCode.valueOf(code);
    }
}