Hash String via SHA-256 in Java

To hash a string, use the built-in MessageDigest class:

import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.nio.charset.StandardCharsets;import java.math.BigInteger;public class CryptoHash {  public static void main(String[] args) throws NoSuchAlgorithmException {    MessageDigest md = MessageDigest.getInstance("SHA-256");    String text = "Text to hash, cryptographically.";    // Change this to UTF-16 if needed    md.update(text.getBytes(StandardCharsets.UTF_8));    byte[] digest = md.digest();    String hex = String.format("%064x", new BigInteger(1, digest));    System.out.println(hex);  }}

In the snippet above, digest contains the hashed string and hex contains a hexadecimal ASCII string with left zero padding.

This is already implemented in the runtime libs.

public static String calc(InputStream is) {    String output;    int read;    byte[] buffer = new byte[8192];    try {        MessageDigest digest = MessageDigest.getInstance("SHA-256");        while ((read = is.read(buffer)) > 0) {            digest.update(buffer, 0, read);        }        byte[] hash = digest.digest();        BigInteger bigInt = new BigInteger(1, hash);        output = bigInt.toString(16);        while ( output.length() < 32 ) {            output = "0"+output;        }    }     catch (Exception e) {        e.printStackTrace(System.err);        return null;    }    return output;}

In a JEE6+ environment one could also use JAXB DataTypeConverter:

import javax.xml.bind.DatatypeConverter;String hash = DatatypeConverter.printHexBinary(            MessageDigest.getInstance("MD5").digest("SOMESTRING".getBytes("UTF-8")));

You don't necessarily need the BouncyCastle library. The following code shows how to do so using the Integer.toHexString function

public static String sha256(String base) {    try{        MessageDigest digest = MessageDigest.getInstance("SHA-256");        byte[] hash = digest.digest(base.getBytes("UTF-8"));        StringBuffer hexString = new StringBuffer();        for (int i = 0; i < hash.length; i++) {            String hex = Integer.toHexString(0xff & hash[i]);            if(hex.length() == 1) hexString.append('0');            hexString.append(hex);        }        return hexString.toString();    } catch(Exception ex){       throw new RuntimeException(ex);    }}

Special thanks to user1452273 from this post: How to hash some string with sha256 in Java?

Keep up the good work !