SHA-256

	public String sha256(String string) {
        MessageDigest md;
		try {
			md = MessageDigest.getInstance("SHA-256");
	        md.update(string.getBytes());

	        byte byteData[] = md.digest();

	        //convert the byte to hex format method 2
	        StringBuffer hexString = new StringBuffer();
	    	for (int i=0;i<byteData.length;i++) {
	    		String hex=Integer.toHexString(0xff & byteData[i]);
	   	     	if(hex.length()==1) hexString.append('0');
	   	     	hexString.append(hex);
	    	}
	    	return hexString.toString();
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
			return null;
		}
	}