Java Streams API provides a powerful and efficient solution for working with collections of data. One common requirement is to merge or concatenate multiple streams into a single stream. In this blog post, we will explore how to accomplish this using the Java Streams API.

Merging Streams

To merge two or more streams into a single stream, we can make use of the Stream.concat() method provided by the java.util.stream.Stream class. This method takes two streams as input and returns a new stream that contains all the elements from both input streams.

Here’s an example that demonstrates how to merge two streams:

import java.util.stream.Stream;

public class StreamMergeExample {
    public static void main(String[] args) {
        Stream<String> stream1 = Stream.of("apple", "banana", "orange");
        Stream<String> stream2 = Stream.of("kiwi", "mango", "pineapple");

        Stream<String> mergedStream = Stream.concat(stream1, stream2);
        mergedStream.forEach(System.out::println);
    }
}

In the above example, we created two streams stream1 and stream2 containing some fruits. We then merged these two streams using the Stream.concat() method. Finally, we printed all the elements of the merged stream using the forEach() method.

Concatenating Streams

In addition to merging streams, we might also need to concatenate streams, where the elements of the second stream follow the elements of the first stream in the resulting stream.

To concatenate two streams, we can use the Stream.of() method along with the flatMap() method.

Here’s an example that demonstrates how to concatenate two streams:

import java.util.stream.Stream;

public class StreamConcatenateExample {
    public static void main(String[] args) {
        Stream<String> stream1 = Stream.of("Hello", "world");
        Stream<String> stream2 = Stream.of("Java", "Streams");

        Stream<String> concatenatedStream = Stream.of(stream1, stream2)
                .flatMap(stream -> stream);
        concatenatedStream.forEach(System.out::println);
    }
}

In the above example, we created two streams stream1 and stream2 with some strings. We then concatenated these two streams using the Stream.of() method and the flatMap() method. Finally, we printed all the elements of the concatenated stream using the forEach() method.

With the techniques explained in this blog post, you can easily merge and concatenate streams in Java Streams API, enabling you to efficiently manipulate and process collections of data.

#java #streaming