MembershipError.java

public class MembershipError extends Exception {
	public MembershipError(String message) {
		super(message);
	}

	public static class JoinRequired extends MembershipError {
		public JoinRequired(String message) {
			super(message);
		}
	}
}

StorageError.java

public class StorageError extends Exception {
	public StorageError(String message) {
		super(message);
	}

	public static class NotFound extends StorageError {
		public NotFound(String message) {
			super(message);
		}

		public static class UndefinedDataFamily extends NotFound {
			public UndefinedDataFamily(String message) {
				super(message);
			}
		}
	}
}

User.java

public class User {
	public static void main(String[] args) throws Exception {
		throw new StorageError.NotFound.UndefinedDataFamily("specified data family is not undefined.");
	}
}