• [Browse Source] (https://github.com/google/google-api-java-client-samples/tree/master/prediction-cmdline-sample), or [main file] (https://github.com/google/google-api-java-client-samples/blob/master/prediction-cmdline-sample/src/main/java/com/google/api/services/samples/prediction/cmdline/PredictionSample.java).

• Enable the Prediction API in the [Google Developers Console] (https://console.developers.google.com/projectselector/apis/api/prediction/overview).
• Create a service account from the [Permissions] (https://console.developers.google.com/permissions/serviceaccounts) page. When you create the service account, select Furnish a new private key and download the service account's private key in P12 format. Later on, after you check out the sample project, you will copy this downloaded file (e.g. MyProject-123456.p12) to the src/main/resources/ directory, and then edit PROJECT_ID, SERVICE_ACCT_EMAIL, and SERVICE_ACCT_KEYFILE in PredictionSample.java.
• [Activate Google Storage] (http://code.google.com/apis/storage/docs/signup.html), upload the training data required by the sample to Google Storage, and then edit OBJECT_PATH in PredictionSample.java to point to the training data. Otherwise, you will get a 400 error "Training data file not found".

Prerequisites: install Java, Git, and Maven. You might need to set your JAVA_HOME.

cd [someDirectory]
git clone https://github.com/google/google-api-java-client-samples.git
cd google-api-java-client-samples/prediction-cmdline-sample
cp ~/Downloads/MyProject-12345abcd.p12 src/main/resources/
[editor] src/main/java/com/google/api/services/samples/prediction/cmdline/PredictionSample.java
mvn compile
mvn -q exec:java

To enable logging of HTTP requests and responses (highly recommended when developing), take a look at logging.properties.