java 해쉬알고리즘 sha256 사용예제

import java.io.FileInputStream;
import java.security.MessageDigest;
 
public class SHACheckSumExample
{
    public static void main(String[] args)throws Exception
    {
         //sha1 해쉬 :  "SHA1"
        MessageDigest md = MessageDigest.getInstance("SHA-256"); 

        FileInputStream fis = new FileInputStream("c:\\loging.log");
 
        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 method 1
        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("Hex format : " + sb.toString());
 
       //convert the byte to hex format method 2
        StringBuffer hexString = new StringBuffer();
    for (int i=0;i<mdbytes.length;i++) {
      hexString.append(Integer.toHexString(0xFF & mdbytes[i]));
    }
 
    System.out.println("Hex format : " + hexString.toString());
    }
}