以下是一个简单的Java示例，演示如何使用Google Cloud Dataflow API将数据从Google Cloud Storage读取并处理：

import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.dataflow.Dataflow;
import com.google.api.services.dataflow.DataflowScopes;
import com.google.api.services.dataflow.model.*;
import com.google.common.collect.ImmutableList;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class DataflowExample {
  // Replace with your Google Cloud project ID
  private static final String PROJECT_ID = "YOUR_PROJECT_ID";

  // Replace with the name of your Dataflow job
  private static final String JOB_NAME = "my-dataflow-job";

  public static void main(String[] args) throws IOException, InterruptedException {
    // Set up the Google Cloud credentials and API client
    HttpTransport httpTransport = new NetHttpTransport();
    JsonFactory jsonFactory = new JacksonFactory();
    GoogleCredential credential =
        GoogleCredential.getApplicationDefault(httpTransport, jsonFactory)
            .createScoped(Collections.singleton(DataflowScopes.CLOUD_PLATFORM));
    Dataflow dataflow = new Dataflow.Builder(httpTransport, jsonFactory, credential)
        .setApplicationName("MyDataflowApplication")
        .build();

    // Set up the input and output files in Google Cloud Storage
    String inputFilePath = "gs://my-bucket/my-input-file.txt";
    String outputFilePath = "gs://my-bucket/my-output-file.txt";

    // Set up the Dataflow pipeline options
    List<String> arguments = Arrays.asList(
        "--project=" + PROJECT_ID,
        "--runner=DataflowRunner",
        "--input=" + inputFilePath,
        "--output=" + outputFilePath
    );
    PipelineOptions options = PipelineOptionsFactory.fromArgs(arguments.toArray(new String[0]))
        .withValidation()
        .create();

    // Set up the Dataflow job
    Pipeline pipeline = Pipeline.create(options);
    PCollection<String> input = pipeline.apply(TextIO.read().from(inputFilePath));
    PCollection<String> output = input.apply(ParDo.of(new MyDoFn()));
    output.apply(TextIO.write().to(outputFilePath));

    // Submit the Dataflow job to the Google Cloud Dataflow service
    Job job = dataflow.projects().jobs().create(PROJECT_ID, new Job()
        .setName(JOB_NAME)
        .setEnvironment(new Environment()
            .setZone("us-central1-f")
            .setWorkerPool(new WorkerPool()
                .setDiskSizeGb(100)
                .setMachineType("n1-standard-4")
                .setNumWorkers(2))
            .setUserAgent("MyDataflowApplication"))
        .setSteps(Arrays.asList(
            new Step()
                .setName("ReadInputFile")
                .setKind("Read")
                .setInput("gs://my-bucket/my-input-file.txt"),
            new Step()
                .setName("ProcessData")
                .setKind("ParallelDo")
                .setParDo(new ParDoInstruction()
                    .setInput("ReadInputFile")
                    .setOutput("WriteOutputFile")
                    .setUserFn(new UserFunction()
                        .setClassName(MyDoFn.class.getName()))),
            new Step()
                .setName("WriteOutputFile")
                .setKind("Write")
                .setInput("ProcessData")
                .setOutput("gs://my-bucket/my-output-file.txt")
                .setFormat("Text")))))
        .execute();
    System.out.println("Submitted Dataflow job: " + job.getId());

    // Wait for the Dataflow job to complete
    while (true) {
      String status = dataflow.projects().jobs().get(PROJECT_ID, job.getId()).execute().getCurrentState();
      if (status.equals("JOB_STATE_DONE")) {
        System.out.println("Dataflow job completed successfully.");
        break;
      } else if (status.equals("JOB_STATE_FAILED")) {
        throw new RuntimeException("Dataflow job failed.");
      }
      Thread.sleep(10000);
    }
  }

  private static class MyDoFn extends DoFn<String, String> {
    @ProcessElement
    public void processElement(ProcessContext c) {
      String input = c.element();
      String output = input.toUpperCase();
      c.output(output);
    }
  }
}