Here is an example of how to use the MergedStream class from the Apache Commons IO library:

import org.apache.commons.io.input.MergedStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;

public class Example {
    public static void main(String[] args) throws IOException {
        // Create the input streams to be merged
        ByteArrayInputStream stream1 = new ByteArrayInputStream("Hello ".getBytes());
        ByteArrayInputStream stream2 = new ByteArrayInputStream("world!".getBytes());
        ByteArrayInputStream stream3 = new ByteArrayInputStream(" This is an example.".getBytes());

        // Create the MergedStream
        MergedStream mergedStream = new MergedStream(stream1, stream2, stream3);

        // Read the data from the MergedStream
        int data = mergedStream.read();
        while (data != -1) {
            System.out.print((char) data);
            data = mergedStream.read();
        }
        // Close the MergedStream
        mergedStream.close();
    }
}

In this example, the MergedStream class is being used to merge three input streams, stream1, stream2, and stream3 into a single stream. The MergedStream reads data from the input streams in the order they are passed in its constructor. The data read from the MergedStream is then printed.

The MergedStream class can be useful when you have multiple small input streams and you want to treat them as a single input stream. This can be helpful for example when you want to concatenate multiple files into a single stream and then process them as a single file.

It's worth noting that the MergedStream class also accepts an array of InputStream as parameter, so you can merge as many streams as you want.