Java Streams API provides a powerful way to work with collections and perform various operations on data. While Java Streams provide many built-in stream sources like lists and arrays, sometimes we may need to create our own custom stream sources.

In this blog post, we will explore how to create custom stream sources in Java Streams API, allowing us to process data from non-traditional sources.

Background

Before we dive into creating custom stream sources, let’s quickly recap what streams are in Java. Streams are a sequence of elements that can be processed in a declarative manner. They provide a way to perform filter, map, and reduce operations on data in a concise and readable way.

By default, Java Streams API provides stream sources for collections like List and Set, arrays, and several other data types. However, there might be scenarios where we want to work with data from non-traditional sources such as databases, web services, or even custom data sources.

Creating Custom Stream Sources

To create a custom stream source in Java Streams API, we need to implement the BaseStream interface, which provides the basic functionalities required to work with streams. Here are the steps to create a custom stream source:

1. Implement the BaseStream interface for your custom data source.
2. Override the necessary methods like iterator() or spliterator() to provide access to the data.
3. Use your custom stream source to perform stream operations like filtering, mapping, or reducing.

Let’s illustrate the steps with an example. Suppose we have a custom data source that provides a stream of integers:

public class CustomStreamSource implements BaseStream<Integer, CustomStreamSource> {

    private final List<Integer> data;

    public CustomStreamSource(List<Integer> data) {
        this.data = data;
    }

    @Override
    public Iterator<Integer> iterator() {
        return data.iterator();
    }

    @Override
    public Spliterator<Integer> spliterator() {
        return data.spliterator();
    }

    // Other methods of the BaseStream interface

}

In the above code snippet, we have implemented the iterator() and spliterator() methods to provide access to the stream data. The CustomStreamSource class can now be used as a source to create Java Streams and perform various operations on the data.

To use our custom stream source, we can create an instance of it and then chain operations like filtering, mapping, or reducing:

public class Main {

    public static void main(String[] args) {
        List<Integer> data = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

        CustomStreamSource customStreamSource = new CustomStreamSource(data);

        customStreamSource
            .filter(num -> num % 2 == 0)
            .map(num -> num * num)
            .forEach(System.out::println);
    }
}

In the above example, we create an instance of CustomStreamSource using a list of integers as the underlying data source. We then perform stream operations like filtering and mapping. Finally, we print the resulting stream elements using the forEach method.

Conclusion

Creating custom stream sources in Java Streams API allows us to work with data from non-traditional sources and apply stream operations on it. By implementing the BaseStream interface, we can provide access to our custom data and leverage the power of Java Streams to process it efficiently.

While creating custom stream sources might not be required in most scenarios, it can be useful when dealing with unique data sources or when integrating with external systems.

#Java #StreamsAPI