How to use update and reset method of CRC32

In this tutorial you will see how to use update and reset method of CRC32.

In this tutorial you will see how to use update and reset method of CRC32.

How to use update and reset method of CRC32.

In this tutorial, we will discuss about the update() and reset() method of CRC32 class. The
CRC32 class is used to compute the checksum of data stream. The CRC32 class is available in
java.util.zip package .

In this example, you will see how to update the CRC32 checksum. The FileInputStream class create
input stream for reading bytes from file. The read() method of FileInputStream class read bytes from
this input stream and store it into a array of bytes. ThegetValue() method of the CRC32 class returns
the value of checksum. The update(byte[] buffer, int offset, int length) method of the CRC32 class
update the value of checksum with array of bytes, and the reset() method of the CRC32 class reset
the checksum value with initial value.

About Adler32 API:

The java.util.zip.Adler32 class extends java.lang.Object class. It provide following methods:

Return Type	Method	Description
checksum	getValue()	The getValue() method returns value of checksum.
void	update(byte[] buff, int offset, int length)	The update() method update checksum with array of bytes.
void	reset()	The reset() method reset the checksum value at initial value.

Code


import java.util.zip.CRC32;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;



class CrcCheckSum {

  public static void main(String[] args) {

    try {

FileInputStream inputStream = new FileInputStream("testfile.txt");

      CRC32 crcChecksum = new CRC32();

      long initialValue = crcChecksum.getValue();

      System.out.println("Initial value of CRC32 checkSum :"

          + initialValue);

      byte[] b = new byte[128];

      while (inputStream.read(b) >= 0) {

      }

      crcChecksum.update(b, 0, b.length);

      long update = crcChecksum.getValue();

    System.out.println("After updating the value of  check sum : "

          + update);

      crcChecksum.reset();

      long resetValue = crcChecksum.getValue();

        System.out.println("Value of CRC32 CheckSum after reset :"

          + resetValue);

    } catch (IOException e) {

      System.out.println("IOException : " + e);

    }

  }

}

Following is the output if you run the application :

C:\>java CrcCheckSum
Initial value of CRC32 checkSum :0
After updating the value of CRC32 checksum : 2141301436
Value of CRC32 CheckSum after reset :0

Download this code

Ads