Is the word japonês the same in Brazilian and European Portuguese?

Yes

The only difference between "japonês" in Brazilian Portuguese and Continental Portuguese is its pronunciation. In Brazil, the "s" at the end of the word is typically pronounced as a voiceless alveolar fricative [s], similar to the "s" in "sun." In Portugal, the "s" at the end of words is generally pronounced as a voiceless postalveolar fricative [ʃ], similar to the "sh" in "shoe." The spelling, meaning, and grammatical usage remain identical.

Brazilian Portuguese Examples

1. Eu adoro comida japonesa. (I love Japanese food.)
2. Ele é um estudante japonês muito dedicado. (He is a very dedicated Japanese student.)
3. Eu estou comendo sushi japonês agora. (I am eating Japanese sushi right now.)
4. O restaurante japonês é muito bom. (The Japanese restaurant is very good.)
5. Ela está aprendendo japonês na escola. (She is learning Japanese at school.)

Continental Portuguese Examples

1. Eu adoro comida japonesa. (I love Japanese food.)
2. Ele é um estudante japonês muito dedicado. (He is a very dedicated Japanese student.)
3. Eu estou a comer sushi japonês agora. (I am eating Japanese sushi right now.)
4. O restaurante japonês é muito bom. (The Japanese restaurant is very good.)
5. Ela está a aprender japonês na escola. (She is learning Japanese at school.)