When using the Gmail API, I want to use a service account to simulate my email and operate my inbox, thereby bypassing the user’s manual authorization operations. Is it possible to implement the postgraduate entrance examination? Can anyone help me?

there is my code

      HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
        GoogleCredential  credential = new GoogleCredential.Builder()
                .setTransport(httpTransport)
                .setJsonFactory(jsonFactory)
                .setServiceAccountId(SERVICE_ACCOUNT_EMAIL)
                .setServiceAccountPrivateKeyFromP12File(GmailServiceAccountExample.class.getResourceAsStream(CREDENTIALS_FILE_PATH))
                .setServiceAccountScopes(Collections.singletonList(GmailScopes.MAIL_GOOGLE_COM))
                .setServiceAccountUser(USER_EMAIL)
                .build();

But encountered the following problem：
com.google.api.client.auth.oauth2.TokenResponseException: 401 Unauthorized POST https://oauth2.googleapis.com/token at com.google.api.client.auth.oauth2.TokenResponseException.from(TokenResponseException.java:103) at com.google.api.client.auth.oauth2.TokenRequest.executeUnparsed(TokenRequest.java:308) at com.google.api.client.auth.oauth2.TokenRequest.execute(TokenRequest.java:324) at com.google.api.client.googleapis.auth.oauth2.GoogleCredential.executeRefreshToken(GoogleCredential.java:378) at com.google.api.client.auth.oauth2.Credential.refreshToken(Credential.java:470) at com.google.api.client.auth.oauth2.Credential.intercept(Credential.java:201) at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:880) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:525) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:466) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:576) at cn.hzj.gamil.example.GmailServiceAccountExample.listMessages(GmailServiceAccountExample.java:73) at cn.hzj.gamil.example.GmailServiceAccountExample.main(GmailServiceAccountExample.java:39)