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Java SequenceInputStream Tutorial with Examples

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1- SequenceInputStream

SequenceInputStream allows you to concatenate two or multiple InputStreams together. It reads from the first byte to the last byte of the first InputStream, then does the same with the next InputStream until the last InputStream.
SequenceInputStream is a subclass of InputStream:
SequenceInputStream​ Methods

final void nextStream() throws IOException  

// Methods inherited from InputStream

public int available() throws IOException  
public int read() throws IOException  
public int read(byte b[], int off, int len) throws IOException  
public int read(byte[] b) throws IOException  
public byte[] readAllBytes() throws IOException  
public byte[] readNBytes(int len) throws IOException  
public int readNBytes(byte[] b, int off, int len) throws IOException  

public long skip(long n) throws IOException

public boolean markSupported()
public synchronized void mark(int readlimit)

public synchronized void reset() throws IOException  
public void close() throws IOException

public long transferTo(OutputStream out) throws IOException
Most of the methods of SequenceInputStream are inherited from InputStream, so you can learn how to use these methods in the article about InputStream.
SequenceInputStream​ Constructors

public SequenceInputStream​(InputStream s1, InputStream s2)    

public SequenceInputStream​(Enumeration<? extends InputStream> e)

2- Examples

Suppose we have two UTF-8 encoded text files, each file contains a list of flower names.
flowers-1.txt

# Flower names (1)

Tulip
Daffodil
Poppy
Sunflower
Bluebell
Rose
Snowdrop
Cherry blossom
flowers-2.txt

# Flower names (2)

Orchid
Iris
Peony
Chrysanthemum
Geranium
Lily
Lotus
Water lily
Dandelion
Hyacinth
Daisy
Crocus
We will read the above 2 files using SequenceInputStream, InputStreamReader and BufferedReader.
SequenceInputStreamEx1.java

package org.o7planning.sequenceinputstream.ex;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.SequenceInputStream;

public class SequenceInputStreamEx1 {

    // Windows: C:/Data/test/flowers-1.txt
    private static String file_path1 = "/Volumes/Data/test/flowers-1.txt";
    private static String file_path2 = "/Volumes/Data/test/flowers-2.txt";

    public static void main(String[] args) throws IOException {

        InputStream is1 = new FileInputStream(file_path1);
        InputStream is2 = new FileInputStream(file_path2);
        
        // Create SequenceInputStream:
        InputStream is = new SequenceInputStream(is1, is2);
        
        InputStreamReader isr = new InputStreamReader(is, "UTF-8");
        BufferedReader br = new BufferedReader(isr);
        
        String line;
        while((line = br.readLine())!= null)  {
            System.out.println(line);
        }
        br.close();
    }
}
Output:

# Flower names (1)

Tulip
Daffodil
Poppy
Sunflower
Bluebell
Rose
Snowdrop
Cherry blossom
# Flower names (2)

Orchid
Iris
Peony
Chrysanthemum
Geranium
Lily
Lotus
Water lily
Dandelion
Hyacinth
Daisy
Crocus
Improve the example above, just print out the line that is not empty and not a comment line (Start with "#").
SequenceInputStreamEx2.java

package org.o7planning.sequenceinputstream.ex;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.SequenceInputStream;

public class SequenceInputStreamEx2 {

    // Windows: C:/Data/test/flowers-1.txt
    private static String file_path1 = "/Volumes/Data/test/flowers-1.txt";
    private static String file_path2 = "/Volumes/Data/test/flowers-2.txt";

    public static void main(String[] args) throws IOException {

        InputStream is1 = new FileInputStream(file_path1);
        InputStream is2 = new FileInputStream(file_path2);
        
        // Create SequenceInputStream:
        InputStream is = new SequenceInputStream(is1, is2);
        
        InputStreamReader isr = new InputStreamReader(is, "UTF-8");
        BufferedReader br = new BufferedReader(isr);
        
        br.lines() // Stream
           .filter(line -> !line.isBlank()) // Not blank
           .filter(line -> !line.startsWith("#")) // Not start with "#"
           .forEach(System.out::println);
        
        br.close();
    }
}
Output:

Tulip
Daffodil
Poppy
Sunflower
Bluebell
Rose
Snowdrop
Cherry blossom
Orchid
Iris
Peony
Chrysanthemum
Geranium
Lily
Lotus
Water lily
Dandelion
Hyacinth
Daisy
Crocus

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