SequenceInputStream

SequenceInputStream class is used to combine two or more input streams into a single combined input stream and reads data out of this combined input stream.

Constructors :

SequenceInputStream(InputStream is1, InputStream is2)
This constructor takes two InputStream objects in the parameters and combine these two input streams into one input stream for reading. Example-: `FileInputStream fis1 = new FileInputStream("D:\\TextBook1.txt"); FileInputStream fis2 = new FileInputStream("D:\\TextBook2.txt"); SequenceInputStream sis = new SequenceInputStream(fis1, fis2);`

The first FileInputStream reference, fis1 points to file D:\\TextBook1.txt, second FileInputStream reference, fis2 points to D:\\TextBook2.txt. According to the order of FileInputStream references in the call to constructor of SequenceInputStream class, file referenced by fis1 will be read before the file referenced by fis2.

Point to remember

FileIntputStream is a subclass of InputStream

Methods for reading SequenceInputStream

Some methods that we generally use while working with SequenceInputStream are shown in the table below :

Methods	Description
available()	This method gives the remaining number of bytes available to read from this input stream.
read()	This method reads one byte at a time from this input stream.
read(byte[])	This method reads a whole byte array at a time from this input stream.
close()	This method closes this input stream and also frees any resources connected with this input stream.

Reading a sequence of two files using SequenceInputStream

The first InputStream reference, fis1 points to file D://TextBook1.txt
The second InputStream reference, fis2 points to D://TextBook2.txt.

Let's say a file TextBook1.txt already exists in D: drive, with the contents -: Let us learn
Let's say a file TextBook2.txt already exists in D: drive, with the contents -: -Java.

//Program to create a SequenceInputStream to combine two streams

import java.io.*;
class A
{
public static void main(String... ar)
{
try
{
FileInputStream fis1= new FileInputStream("D:\\TextBook1.txt");
FileInputStream fis2= new FileInputStream("D:\\TextBook2.txt");


SequenceInputStream sis= new SequenceInputStream(fis1,fis2); //combining the two input streams

int c;

while( (c=sis.read())!=-1)
{
System.out.print((char)c);
}

bos.flush();

fis1.close();
fis2.close();                                                                         
sis.close();
}
catch(IOException e)
{
System.out.println(e);
}

}
}

Output is -:

 Let us learn-Java

Program Analysis

According to the sequence of FileInputStream objects references in the call to constructor of SequenceInputStream class, file referenced by fis1 will be read before the file referenced by fis2.
Data is read(one byte at a time) using read(int b) method of SequenceInputStream class
Finally, all the opened streams are closed by calling their close() method.

Combining two files into one file.

First InputStream object, fis1 points to file "D://TextBook1.txt" and second InptutStream object, fis2 points to "D://TextBook2.txt". This code will use SequenceInputStream class to make a sequence of these two InputStream objects through which data will be read.
A file "TextBook1.txt" already exists in D: drive, with the contents -: Let us learn-
A file "TextBook2.txt" already exists in D: drive, with the contents -: Java.

//Program to create a SequenceInputStream to combine two streams

import java.io.*;
class A
{
public static void main(String... ar)
{
try
{
FileInputStream fis1= new FileInputStream("D:\\TextBook1.txt");
FileInputStream fis2= new FileInputStream("D:\\TextBook2.txt");


SequenceInputStream sis= new SequenceInputStream(fis1,fis2); //combining the two input streams


FileOutputStream fos= new FileOutputStream("TextBook3.txt");
BufferedOutputStream bos= new BufferedOutputStream(fos);

int c;

while( (c=sis.read())!=-1)
{
System.out.print((char)c);
bos.write(c);
}

bos.flush();

fis1.close();
fis2.close();                                                                         
sis.close();
bos.close();
fos.close();
}
catch(IOException e)
{
System.out.println(e);
}

}
}

Output

After the execution of this program, a file "TextBook3.txt" is created in the D: drive, with contents -:
Let us learn-Java.

Program Analysis

According to the sequence of FileInputStream objects in the call to constructor of SequenceInputStream class, file referenced by fis1 will be read before the file referenced by fis2.
Data is read out(one byte at a time) using read(int b) method of SequenceInputStream class
The data which was read, is written out to a file "D://TextBook3.txt" using write(int b) method of BufferedOutputStream object.
Finally the buffer is flushed and all opened streams are closed by calling their close() method.

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