How to generate a file checksum value in Java

package org.best.example; 

import java.io.FileInputStream;
import java.security.MessageDigest;
 
public class TestCheckSum {
 
  public static void main(String args[]) throws Exception {
 
    String datafile = "c:\\INSTLOG.TXT";
 
    MessageDigest md = MessageDigest.getInstance("SHA1");
    FileInputStream fis = new FileInputStream(datafile);
    byte[] dataBytes = new byte[1024];
 
    int nread = 0; 
 
    while ((nread = fis.read(dataBytes)) != -1) {
      md.update(dataBytes, 0, nread);
    };
 
    byte[] mdbytes = md.digest();
 
    //convert the byte to hex format
    StringBuffer sb = new StringBuffer("");
    for (int i = 0; i < mdbytes.length; i++) 

{
 sb.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1));
    }
 
    System.out.println("Digest(in hex format):: " + sb.toString());
 
  }
}