Java.io.ByteArrayInputStream class in Java

ByteArrayInputStream class of java.io package contains all the buffers, containing bytes to be read from the Input Stream. There is no IO exception in case of ByteArrayInputStream class methods. Methods of this class can be called even after closing the Stream, there is no effect of it on the class methods. The class view is as follows: 

--> java.io Package
    --> ByteArrayInputStream Class   

Syntax:

public class ByteArrayInputStream
extends InputStream

There are certain Fields:

• protected byte[] buf: An array of bytes that was provided by the creator of the stream.
• protected int count: The index one is greater than the last valid character in the input stream buffer.
• protected int mark: The currently marked position in the stream.
• protected int pos: This is the index of the next character to read from the input stream buffer.

Constructor of ByteArrayInputStream Class

Constructor	Action Performed
ByteArrayInputStream(byte[] buffer)	It creates ByteArrayInputStream to use buffer array – “buffer”.
ByteArrayInputStream(byte[] buf, int offset, int length)	It creates ByteArrayInputStream that uses some part of “buffer” i.e. buffer array

Methods of ByteArrayInputStream class

Method	Action Performed
available()	It tells the total number of bytes from the input stream to be read.
close()	It closes the input stream and releases system resources.
mark()	It marks the current position of the input stream which means setting the read limit.
markSupported()	It tests if this input stream supports the mark and reset method.
read()	It reads the next byte of data from the input stream.
reset()	It repositions the input stream to the marked position and is called the mark() method
skip()	Skips the “args” in the input stream.

Implementation:

Java

// Java Program to Demonstrate ByteArrayInputStream Class
// Via mark(), read(), skip(), available(),
// markSupported(), close(), reset() Method

// Importing required classes
import java.io.*;

// Main class
public class GFG {

    // Main driver method
    public static void main(String[] args) throws Exception
    {

        // Declaring and initializing byte array
        byte[] buffer = { 71, 69, 69, 75, 83 };
        ByteArrayInputStream geek = null;

        // Try block to check for exceptions
        try {
            geek = new ByteArrayInputStream(buffer);

            // Telling the no. of bytes to be read
            // using available() method
            int number = geek.available();
            System.out.println(
                "Use of available() method : " + number);

            // Reading and printing Characters one by one
            // using read() method
            System.out.println("\nChar : "
                               + (char)geek.read());
            System.out.println("Char : "
                               + (char)geek.read());
            System.out.println("Char : "
                               + (char)geek.read());

            // Usage of mark() method
            geek.mark(0);

            // Skipping 'k' from "GEEKS"
            // using skip() method
            geek.skip(1);
            System.out.println(
                "skip() method comes to play");
            System.out.println(
                "mark() method comes to play");
            System.out.println("Char : "
                               + (char)geek.read());

            // Usage of markSupported() method
            boolean check = geek.markSupported();
            System.out.println("\nmarkSupported() : "
                               + check);

            if (geek.markSupported()) {

                // Repositioning the stream to marked
                // positions using reset() method
                geek.reset();

                System.out.println("\nreset() invoked");
                System.out.println("Char : "
                                   + (char)geek.read());
                System.out.println("Char : "
                                   + (char)geek.read());
            }
            else {
                System.out.println(
                    "reset() method not supported.");
            }

            System.out.println(
                "geek.markSupported() supported reset() : "
                + check);
        }

        // Catch block to handle the exceptions
        catch (Exception except) {

            // Displaying the exception along with line
            // number using printStackTrace() method
            except.printStackTrace();
        }

        // finally block that execute for sure
        finally {

            // Releasing the resources back to GC when
            // closes
            if (geek != null) {

                // Closing the file and releasing resources
                // using close() method
                geek.close();
            }
        }
    }
}

Output

Use of available() method : 5

Char : G
Char : E
Char : E
skip() method comes to play
mark() method comes to play
Char : S

markSupported() : true

reset() invoked
Char : K
Char : S
geek.markSupported() supported reset() : true