private static final ClientCredentialsRequest ccr = api.clientCredentials()
        .build();

public static void getClientCredentials() {
    try {
        final ClientCredentials clientCredentials = ccr.execute();
        api = new SpotifyApi.Builder()
                .setAccessToken(clientCredentials.getAccessToken())
                .build();
        System.out.println("Expires in: " + clientCredentials.getExpiresIn() + "\n" +
                "Access Token: " + clientCredentials.getAccessToken());
    } catch (IOException | SpotifyWebApiException | ParseException e) {
        System.out.println("Error: " + e.getMessage());
    }
}

static final GetArtistRequest getArtistRequest = api.getArtist("4MCBfE4596Uoi2O4DtmEMz")
        .build();

public static void main(String[] args) {
    getClientCredentials();

    try {
        final Artist a = getArtistRequest.execute();
        System.out.println("Name: " + a.getName());
    } catch (Exception e) {
        System.out.println("Something went wrong!\n" + e.getMessage());
    }
}