Command.java

enum Command {
    NEW_PERSON {
        final char KEY = 'P';
    },
    ADD_FRIEND {
        final char KEY = 'A';
    },
    UNFRIEND {
        final char KEY = 'U';
    },
    LIST_FRIENDS {
        final char KEY = 'L';
    },
    QUERY_FRIENDS {
        final char KEY = 'Q';
    },
    EXIT {
        final char KEY = 'X';
    };
}