//the method, I hash the typed password:
private String getSHA2(String str) {
	MessageDigest md;
	try {
		md = MessageDigest.getInstance("SHA-256");
		md.update(str.getBytes());
			byte byteData[] = md.digest();
			// convert the byte to hex format method 1
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < byteData.length; i++) {
			sb.append(Integer.toString((byteData[i] & 0xff) + 0x100, 16)
					.substring(1));
		}
		return sb.toString();
	} catch (NoSuchAlgorithmException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
	return null;
}
 
 
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//the method to check the hashed pw against the password, saved in the Database
public static int checkPW(String username, String pw) {
		try {
			open_static_Connection();
			PreparedStatement sqlGetUserPW = static_con
					.prepareStatement(select_user_id);
			sqlGetUserPW.setString(1, username);
 
			ResultSet rsUser = sqlGetUserPW.executeQuery();
 
			while (rsUser.next()) {
				java.sql.Clob obj = rsUser.getClob("password");
				String str = obj.getSubString(1, (int) obj.length());
				System.out.println("str " + str);
 
				if (pw.equals(str)) {
					return rsUser.getInt("uid");
				} else
					return -1;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return -1;
	}