Good way to replace invalid characters in firebase keys?

Question

My use case is saving a user\'s info. When I try to save data to Firebase using the user\'s email address as a key, Firebase throws the following error:

Answer 1

I am using the following code for converting email to hash and then using the hash as key in firebase

public class HashingUtils {
    public HashingUtils() {
    }

    //generate 256 bits hash using SHA-256
    public String generateHashkeySHA_256(String email){
        String result = null;
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] hash = digest.digest(email.getBytes("UTF-8"));
            return byteToHex(hash); // make it printable
        }catch(Exception ex) {
            ex.printStackTrace();
        }
        return result;
    }

    //generate 160bits hash using SHA-1
    public String generateHashkeySHA_1(String email){
        String result = null;
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-1");
            byte[] hash = digest.digest(email.getBytes("UTF-8"));
            return byteToHex(hash); // make it printable
        }catch(Exception ex) {
            ex.printStackTrace();
        }
        return result;
    }

    public String byteToHex(byte[] bytes) {
        Formatter formatter = new Formatter();
        for (byte b : bytes) {
            formatter.format("%02x", b);
        }
        String hex = formatter.toString();
        return hex;
    }
}

code for adding the user to firebase

public void addUser(User user) {
    Log.d(TAG, "addUser: ");
    DatabaseReference userRef= database.getReference("User");

    if(!TextUtils.isEmpty(user.getEmailId())){
       String hashEmailId= hashingUtils.generateHashkeySHA_256(user.getEmailId());
        Log.d(TAG, "addUser: hashEmailId"+hashEmailId);
        userRef.child(hashEmailId).setValue(user);
    }
    else {
        Log.d(TAG,"addUser: empty emailId");
    }
}