pipeline java

Pipeline in Java refers to the concept of creating a sequence of operations that can be executed one after another to process data. It's commonly used in functional programming and Apache Beam, a distributed processing framework, where it enables developers to define complex data processing pipelines as a series of stages.

Here's a simple example of how you might use a pipeline in Java:

import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.TextIO;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.ParDo;

public class WordCount {
    public static void main(String[] args) {
        // Create a new Pipeline options instance
        PipelineOptions options = PipelineOptionsFactory.create();

        // Create a new Pipeline with the given options
        Pipeline pipeline = Pipeline.create(options);

        // Read input text from a file
        String input = "input.txt";
        PCollection<String> lines = pipeline.read(TextIO.from(input));

        // Apply a ParDo transform to tokenize the words
        PCollection<String> words = lines.apply(ParDo.of(new TokenizerFn()));

        // Count the occurrences of each word
        PCollection<KV<String, Long>> counts = words.apply(Count.perElement());

        // Write the result to an output file
        String output = "output.txt";
        counts.writeTo(TextIO.to(output));

        // Run the pipeline
        pipeline.run().waitUntilFinish();
    }
}

// Custom DoFn for tokenizing words
class TokenizerFn extends DoFn<String, String> {
    @ProcessElement
    public void process(@Element String line, OutputReceiver<String> receiver) {
        String[] tokens = line.split("\\s+");
        for (String token : tokens) {
            receiver.output(token);
        }
    }
}

In this example, a `Pipeline` is created, which reads text from a file, tokenizes the words using a custom `TokenizerFn`, counts the occurrences of each word, and finally writes the results to an output file.