我已经为谷歌凭据设置了环境变量，但我不知道下一步是什么。请帮我解决这个错误
The Application Default Credentials are not available. They are available if running in Google Compute Engine. Otherwise, the environment variable GOOGLE_APPLICATION_CREDENTIALS must be defined pointing to a file defining the credentials. See https://developers.google.com/accounts/docs/application-default-credentials for more information.
at com.google.auth.oauth2.DefaultCredentialsProvider.getDefaultCredentials(DefaultCredentialsProvider.java:119)
at com.google.auth.oauth2.GoogleCredentials.getApplicationDefault(GoogleCredentials.java:127)
at com.google.auth.oauth2.GoogleCredentials.getApplicationDefault(GoogleCredentials.java:100)
at com.google.api.gax.core.GoogleCredentialsProvider.getCredentials(GoogleCredentialsProvider.java:53)
at com.google.api.gax.rpc.ClientContext.create(ClientContext.java:134)
at com.google.cloud.vision.v1.stub.GrpcImageAnnotatorStub.create(GrpcImageAnnotatorStub.java:61)
at com.google.cloud.vision.v1.stub.ImageAnnotatorStubSettings.createStub(ImageAnnotatorStubSettings.java:93)
at com.google.cloud.vision.v1.ImageAnnotatorClient.<init>(ImageAnnotatorClient.java:131)
at com.google.cloud.vision.v1.ImageAnnotatorClient.create(ImageAnnotatorClient.java:112)
at com.google.cloud.vision.v1.ImageAnnotatorClient.create(ImageAnnotatorClient.java:103)
at com.example.vision.QuickstartSample.main(QuickstartSample.java:42)
