In this tutorial we are going to see how to generate a file’s Checksum value in Java using the SHA-1 hash function. If you are working on your applications security specs it might be useful to consider using checksums to improve the security and integrity of file transfer or file sharing actions.
In short, the basic steps one should take in order to calculate the checksum value of a file are:
- Create an
MessageDigestinstance with the SHA-1 function usingMessageDigest.getInstance("SHA1")method. - Open and read the file using a
FileInputStream. - Update the MessaDigest with the new bytes you read from the file using
MessageDigest.updatemethod - Then use a
StringBufferto convert and print theMessageDigestin hex representation.
Let’s take a look at the code:
package com.javacodegeeks.java.core;
import java.io.FileInputStream;
import java.security.MessageDigest;
public class FileCheckSumExample {
public static void main(String args[]) throws Exception {
String filepath = "C:\\Users\\nikos7\\Desktop\\output.txt";
MessageDigest messageDigest = MessageDigest.getInstance("SHA1");
FileInputStream fileInput = new FileInputStream(filepath);
byte[] dataBytes = new byte[1024];
int bytesRead = 0;
while ((bytesRead = fileInput.read(dataBytes)) != -1) {
messageDigest.update(dataBytes, 0, bytesRead);
}
byte[] digestBytes = messageDigest.digest();
StringBuffer sb = new StringBuffer("");
for (int i = 0; i < digestBytes.length; i++) {
sb.append(Integer.toString((digestBytes[i] & 0xff) + 0x100, 16).substring(1));
}
System.out.println("Checksum for the File: " + sb.toString());
fileInput.close();
}
}
Output
Checksum for the File: 89168dc12b380ab3c84917bc5a8a6c6e9452da1f
This was an example on how to generate the checksum value of a File in Java.
